Streetwind

This should have the answer you're looking for:
 

You will not be able to grow the same type of crop on the same block of farmland over and over.
Each crop requires one of the three nutrients, and drains it from the soil. The less nutrient remains, the slower the crop grows. Nutrient recovers over time, but much slower than plants consume it. Fertilizer helps, but releases only gradually over time (hence the tooltip literally saying "slow-release fertilizer"). Some crops with high nutrient needs will still drain the soil much faster than fertilizer can restore it.
To get around this, you need crop rotation. That means: first, plant a K crop. Once its fully grown and harvested, plant a N crop. Once that's fully grown and harvested, plant a P crop. And once that is done, the K nutrient will have fully recovered and you can start again from the beginning. You don't even need fertilizer or good soil for this to work. If you do have good soil and fertilizer, you may be able to alternate between just two crop types instead of all three.
But you can't expect to just plant flax over and over without a break on the same soil. This is intentional.

Pretty sure this is hardcoded.

Less valuable items will typically be traded in multiples.
That is, he may show "8 feathers", and have a demand of "2", meaning he's buying two stacks of eight feathers each. Since you only offer two feathers, you're not even offering one stack, so there can be no trade.
Therefore, doublecheck the stack size of the offer.

I think the location is unique. So just one per world.

Flax has a temperature tolerance of -5°C. The greenhouse makes the plant treat the ambient temperature as 5°C higher, so effectively it can go to -10°C now.
Your ambient temperature dropped below -10°C at some point, and the plant got cold damaged.
Once the plant gets damaged, it doesn't recover.

When installing mods on an existing save,
- some mods simply just work, and
- other mods will not work fully because they rely on world/terrain generation to enable their content, but
- no mods will cause problems with your save
When removing mods from an existing save,
- a few will be possible to remove without a trace,
- a few will cause your world to no longer work, and
- most will cause a graceful failure state where they can be removed just fine but leave behind invalid blocks with missing textures

Yes, the calendar pauses while no one is online.

From 1.17.7 forwards, the game will pause when the player opens the handbook in singleplayer mode. This was a much and long requested improvement among the playerbase. (Obviously no change in behavior in multiplayer).
Perhaps your nephew used to open the handbook to let the world generate? But no, that wouldn't have been a true and proper pause in old versions, meaning that time would pass, the character would grow hungry, and enemies could attack the player. So it can't have been that.
The choose-your-character screen was also upgraded from simply freezing the ingame time progression (which still left you vulnerable to attacks and hunger) to a true pause in one of the more recent versions. Can't for the life of me remember which one though.
I just tested in 1.15.9, which is the oldest version I still have lying around. Even back then, a true pause did not allow world generation to proceed in the background; everything is completely stopped. So whatever your nephew used, it was never a true pause. Just something that felt like it. Probably the character creation screen.
 

Right. Regarding fruit trees, the most temperature-sensitive of the tropics trees start having a chance to die once the temperature drops to below +10°C. I don't think it happens immediately upon reaching that temperature; it's probably more something like being below that temperature for a full day. Also, it is possible for the tree to survive down to +6°C, although the chance grows smaller the colder it gets.
Meanwhile, the non-tropics trees need vernalization, and for that to trigger, multiple full days need to pass without the temperature ever climbing above +1.5°C at any point. There's a chance it might still work up to +2.5°C, but for guaranteed fruiting you want a degree below that. And remember, it must not rise above that temp at any point, so that would limit the daily maximum only; daily minimum during the same time will probably be -15°C or even lower. And that's a big problem for the tropics trees, as you can imagine.
Placing a fruit tree into a greenhouse will allow it to vernalize more easily. The +5°C greenhouse bonus is applied to vernalization temperature. It is not, however, applied to any other temperature governing fruit trees.
Peach trees have a die-below temperature of only -12°C, but still need vernalisation, so those are the hardest to cultivate out of all trees. The climate where that works out is a much narrower band than for the other trees. But greenhouses can help here.
All other vernalizing trees can go much colder, and you basically don't need to worry about their survival at all unless you move northwards from spawn. But since you want to accomodate tropics trees, you'll be moving south, and trying to find an area where tropics trees can thrive at sea level while planting vernalizing trees far up a mountain.
 

Each bloomery does 120 nuggets (5 blooms) at a time, yeah.
The solution is moar bloomeries. I typically do two or three in parallel when I work iron, but I only smelt some when I need it. I have never tried to smelt a whole iron vein all at once - I value my sanity Processing those blooms without at least four helvehammers would take ages, and I can't be bothered to build that many when one or two will cover my actual needs.
But if I tried to do mass-smelting... Well, I'd crush all my ore into nuggets, and then count the number of slots taken up by those nuggets. 1 slot holds 128, a bloomery holds 120, so it's a good first order approximation to build one bloomery per slot. Whatever's left over can go into a second run. It'll likely be done well before you get the blooms from the first run processed.
One bloomery happens to take 12 fire clay bricks, and you fire clay bricks in sets of 12... so you just fill one pit kiln with bricks for every bloomery you want to build.
You also get like 8-10 bricks back when you break a bloomery, so you can use those in a second run for whatever ore you'll have left over.

Quoting from the patch notes:
What exactly hasn't been working for you?

Known issue with 1.18.5. Fix is pending for 1.18.6.

For the lower tier enemies, using a shield and just taking the blow is great. Neither surface drifters nor deep drifters nor bronze locusts deal enough damage to overcome a raised shield, so you just watch them flail ineffectually and laugh as you murder them. Even tainted drifters only deal minor damage.
For stronger enemies - sawblade locusts, bears, nightmare drifters - you want to dodge and kite. They have too much HP to kill them quickly, deal a lot of damage even past a shield, and can often shred armor at accelerated rates. In that case, you have to time your strikes just right, so that the moment where the hit happens you are in range and then immediately retreat. You can use a bronze spear in melee to make this easier, because the spear has a longer range, so you have more safety margin; but it also does a lot less damage than a high-tier falx, so it's not ideal either. Ideally you'd bring a good bow, or even a sling with several stacks of stones.

Hostile creature spawning in VS works a lot like in Minecraft: wherever the light level is low enough, drifters can spawn.
When rifts were introduced, VS added an additional rule on top: drifter spawning is forbidden under the open sky. Only places that have a solid block above them qualify for spawning (given appropriately low light level). Rifts break this rule, allowing drifters to spawn under the open sky in a small radius around them.
When you turn off rifts, you simply turn off this extra rule and revert the game to Minecraft behavior: drifters can spawn anywhere the light level is low enough, even under the open sky. There is no setting that turns off hostile creature spawning.
However, with creatureHostility=off, these creatures should not attack you.
Additionally, there may be mods available that remove hostile creatures entirely. Click the "Mods" button in the navigation bar at the top of the forums to go to the official mod database.
 

This happens when the game saves just as you exit the bed. That stops the time acceleration from smoothly winding down.
To fix this, get back into bed (so that time starts accelerating faster again) and then exit it (so it stops accelerating).

This is new with 1.18, in a way, though not as new as you may think.
Food spoil speed has always scaled with temperature. The hotter it gets - and I notice in your screenshot that it is summer - the more quickly perishables will spoil. In previous versions, storage containers like clay vessels would display only their own modifier to food spoil speed, while the modifier from temperature was applied silently in the background and was not shown anywhere. From 1.18 onwards, storage containers show the sum of all modifiers applying to food stored within.

/worldconfig foodSpoilSpeed 0
Although I'm not sure if 0 is a valid value here. Some of these worldconfigs have minimum lower limits, you'll have to experiment. The closer to 0 you can set it, the slower food will spoil.
After you enter this command, exit to main menu and reload your world, then enter the command again without a number to let it print the currently active value. If you entered something invalid (for example if it doesn't like 0) it will likely display the default value of 1. Then you can try something else, like 0.1.

That "square that indicates the area" is probably drawn by the mod VsProspectorInfo. It is not a feature of the base game.

This is not possible, but you can achieve the same look by using multi-material chiseling.

Not currently, no.

Yes, temperature currently changes at a rate of 0.667°C per block height difference (says Tyron on Discord), colder at high altitudes, warmer at low ones, independent of total world height.
Note: 1.18 is likely to make changes to this formula, as there is a worldgen revamp coming with it.

This is currently under very active discussion on Discord, and a lot of people have a lot of opinions about this.
On one hand, both .NET 4 and Windows 7 are extremely old. Using Win7 with an internet connection in this day and age is a major security risk for the user, and building software on an outdated framework makes that software slower and less safe. .NET 7 in particular has significant performance optimizations under the hood that would really benefit people using older hardware. Additionally, the Steam user survey, which is a fairly representative global sample of PC gamers, suggests that fewer than 2% of all Steam users are still using Windows versions older than Win10.
On the other hand, reducing the scope of supported platforms without prior announcement is a dick move, even with an essentially unlimited refund policy like Vintage Story has. The team is well aware of this, and Tyron aspirationally wants to continue shipping old framework builds for multiple future releases.
On the third hand, shipping multiple builds in parallel is fraught with issues, both when it comes to developing the base game, and when it comes to mod support. Maintaining support for the old framework costs development time that could be spent on improving the game instead. Modders would have to choose between supporting and debugging two separate versions of each of their mods, or to pick just one and not service the other. This risks a split in the modding community that'll get worse the longer the base game decides to maintain support for the outdated framework and Windows versions.
It has been confirmed that 1.18 will be shipping on both .NET 4 and .NET 7. Anything beyond that, nobody knows for sure.
Meanwhile, good lord, update your OS. Please don't tell me you habitually do online banking on this machine...
 

I'm not sure if there is a proper definition of a "solid block" written down anywhere, but in my own experience it is something like:
A block that is no less than half a block thick at any point; and which has a face that is level with a neighboring full block surface, which is the "solid face".
In other words, a full block automatically qualifies. But a solid block can also be a stair or a slab, or even a chiseled block of equal or greater thickness, if it is oriented correctly. For example, a slab that is attached to the upper side of a neighboring block will have its "solid face" (the one level with a full block face) on the top, whereas a slab attached to the bottom side of a neighboring block will have its "solid face" on the bottom.
To build a charcoal pit, it needs an unbroken surface of solid faces on the inside. You can use slabs for this, as long as all the solid faces are pointing inwards. You can use chiseled blocks for this, as long as they are as thick as slabs or thicker, oriented correctly, and not perforated.
Doors and such are not solid, and therefore automatically invalid in the construction of a charcoal pit.
(I can't remember right now whether transparent blocks count or not. I think so, but might be mixing things up with Minecraft here. Or I might be mixing up the mixup. Who knows!)
 

You are not doing anything wrong You are correct to expect magnetite at this location You are somewhat unlucky and lack experience Not all ores are created alike. Indeed, there is a bit of a scale to them, in terms of difficulty of finding them. The common ores, something like copper and bismuthinite, and to some extend even cassiterite? They're easy to find by just going through the motions with the prospecting pick. Hunt down a nice, high peak value with Density Search, dig vertically down in that place, perhaps take the occasional Node Search sample along the way - and you're virtually guaranteed to hit ore. Every time.
But the more exotic and/or advanced ores, they have quirks. Things to know about each of them that inform the way you search and the way you dig for that particular ore. It partially starts with cassiterite, where knowing to dig in a place with all-igneous stone top to bottom will noticeably increase your chances over places with just an igneous bottom layer. And then comes iron - and it's a completely different beast. All of the iron ores, to some extend, but especially magnetite.
You see, to generate ores, the game rolls a number of tries each chunk. It picks a random block within the ore's spawn range in that chunk, and rolls a die against the spawn chance in that location. If you've got an Ultra High reading, the chance to succeed this roll approaches 100%; if you've got a Miniscule reading, it's almost guaranteed to fail (but only almost). When the roll succeeds, the game tries placing an ore vein centered on that block. Now, this may still fail - perhaps it picked an invalid block that cannot host this ore. Or maybe a cave generated later-on might turn everything in that area, including the ore vein, into air. But if the block is the correct host rock, then it and surrounding host rock blocks are replaced by a disc of ore of a certain size, as defined in the ore's spawn config. Then the game rolls another try, up to the number of tries per chunk as defined in the ore's spawn config. It does this for every chunk.
Up to iron, every ore has multiple tries per chunk. Some of them have two-digit tries per chunk. Iron... doesn't. Iron has fewer than one tries per chunk. Magnetite, in particular, sits at an abysmal 0.3 tries per chunk.
Now, when the game goes to roll for a spawn, it has to make two rolls. First it needs to roll whether or not it is even allowed to roll. And with Magnetite, it has a 70% chance to fail this roll. So your Ultra High chunk, where Magnetite has a near guaranteed chance to make its spawn roll? It failed to even be allowed to try. And that's why there isn't anything there, despite what the prospecting indicates.
The takeaway here is that when searching for iron, and magnetite in particular, it's not enough to examine just that one chunk with the highest reading. You need to examine enough chunks to overcome the ore's chance of failing to be allowed to try to spawn. In return, when you do find an iron vein, it's going to be absolutely ginormous and you're unlikely to need to look for another vein for a long, long time.
Iron discs are over fifty blocks in diameter. This means that, since you didn't find any indication of iron in your current shaft despite eight blocks of Node Search range, it is safe for you to go fifty to sixty blocks away to dig another shaft. Continue picking locations with high readings, and/or make some sort of grid around your Ultra High result. You can try closer than fifty blocks, of course, if you're afraid of missing something; but the smaller you make your search grid, the more shafts you may have to dig until you find a vein.