Maelstrom

Hens will spook if you are within 11 blocks of them.  Spooked hens will not brood which will make hatching chicks take longer.   Otherwise, proximity will not impact egg production.

Wiki isn't accurate (mostly outdated) in quite a few things, this being one of them.   I believe gestation period is hardcoded at this time.   Same with berries.   
Hopefully, Tyron will update that.   Soon.   ish.  

Natural light and presence of wood have the biggest impact on a cellar.  Be sure to seal the cellar with a basic door to keep light out.   Also do not use wood flooring or walls.  Shelves and chest/trunks might have a minor negative impact as well.

Yep.   Once rollers are laid out they will not disappear until construction of the boat is completed.  I believe it is because the game uses a "micro dimension" to handle creating the boat.

Multiple veins of iron are possible.   They can even overlap.   Back in 1.16 cleaned out an iron deposit, did some prospecting around the edges to make sure I had gotten the strays and got a medium result on node search.   MEDIUM?! Seriously?!!   Dug up just 5 blocks and hit a second deposit of iron.   @junawood streamed a similar occurrence a few years ago.

Welcome to VS and the forums!
To my understanding, fire clay generating under black coal is possible but not guaranteed.  Given the plentiful deposits of red clay, gather up a stack of flint, bake it, grind it then mix it in with red clay.  You'll get 8 stacks of fire clay.   Best if you use the Better Firepits mod to make baking all that flint easier.  Also automate the quern with a windmill.

Orienteering in vanilla - hopefully it's obvious that clouds travel west to east.   Knapped tools ALWAYS face the same direction, like saaaaayyy the flint spear head I believe points north; regardless of the way one is facing when placing the knappable rock.

Five for the base and four for the top.   I usually have voxels left over for the base but every voxel is needed for the top.  
The last time I forged an anvil I tried putting three or four ingots in place before the never ending pounding began.   Yeeeeaaaahhh, that was a mistake.   Ended up losing voxels in the last ingot.  Moral of the story - place ingots only when needed.  
If you didn't do what I did, you may have deleted misplaced voxels during the process.  If it's in 1.21 it could also be a bug.

Yes.  They just need to be top block flush with the farmland you plant the seed in.
Just till the ground where the seed is planted.  Put a water source diagonal to that block for maximum moisture.  I've heard placing a block on the diagonals of the seed can increase the yield of punkins.

If the bushes are just oppressively overcrowding your plains, might I suggest a... ummm... quick clearing option?
It involves a torch and little a bit of time.
https://tse4.mm.bing.net/th/id/OIP.IHZYuBWmuWm7iKt7CRpyBwAAAA?r=0&rs=1&pid=ImgDetMain&o=7&rm=3
 
Burn, baby, burn!!!

Dig hole 2 blocks deep.  Put small trough with one grain in bottom.  Put baited trap next to trough.

A crop's yield drops according to how long that crop has been exposed to extreme temperatures.  While the first instance (stunted) happens as soon as the temp exceeds the crop's tolerance, the yield doesn't drop to 75% until it spends a total of 24 hours in that extreme temperature.  Other more technical players can confirm or correct as necessary.  Another 24 hours will drop the yield to 50% and so on until the plant just dies completely.

Animals need food for only two things - breeding and increasing weight for slaughter.  Otherwise they will survive and mature if locked in a pure stone box.   How? I've got no freaking clue, but they do.  Magic I guess?  

First - That peat isn't going anywhere.  Unless you set it ablaze which will be darn near impossible once snow covers the ground.  Collect it when you need it.  It's a great source of fuel for pit kilns (faster than firewood as well), just about anything in the firepit except smelting ores or flint.
Animals do not die if they aren't fed.  Feeding does only two things - enable breeding and increase their weight for slaughter.  Animals will forage to keep themselves alive, even if they are confined in a stone building with stone floors.  Somehow those pigs will find enough to stay alive.  

Ohhhh, I see.   Don't know off the top of my head and can't reference the game while at work.  Not sure I'll play tonight after work but next chance I get I'll get that for you.  Alternatively, you could begin creating a new world to get the default and then abort the rest of creating that world..

No.  All items have the same durability regardless of which class crafts it.

Each backpack slot maps to specific spots in your inventory.  The first basket maps to the first three inventory spaces in the top left of your inventory screen.  Having just one item in one of those three spaces will lead to the problem that when the basket is exchanged for a backpack, the item will still be in the basket.  It sounds like the basket with items dropped tot the ground as an entity and then despawned.  
Only two things to do about it now.  Cheat in said items, or take the lumps from the School of Hard Knocks and find another 40 nuggets of copper.

What was the solution?

Wlecome to the forums!!!

Good question.  Caused me to go searching the interwebs with goggle.  And I found that historically speaking, making brass was difficult.  So difficult that it wasn't made until the 1700s.
Since you already have zinc, you may stumble across bismuth and make your way into the bronze age anyway.  😊

animals do not starve.  Feeding is only necessary for getting the females preggers or to fatten aminals up for slaughter.

Granite is the default rock strata and is overridden by other rock types determined by the world gen algorithms.  Since granite is the default rock type there can be vast sprawling expanses of this rock type for mind boggingly large distances.  Finding ANY sedimentary rock in such a vast sea of granite is futile.  It's rare that such massive wastelands of granite exist, but the world gen gods can (and obviously do) conspire to smite us with such copriciousness.  My condolences for your experiences @Sir_Reginald_Duff_III.  May your next world not be the same.

Ores other than iron typically generate multiple deposits, especially in ultra-high readings.  Keep on digging.  Last night I had 2 rich and 1 medium copper vein spawn right next to each other.  Killed 2 bismuth bronze picks during the 60 minute mining.  Walked away with almost 6 stacks of rich copper chunks and 4 stacks of medium chunks.

100 units creates 1 ingot
1 nugget (aka piece) = 5 units
True for all metals.

There is a size limit for images you upload.  You can delete old images through your profile.

It is typical for night to be exceedingly dark.  This is intentional by the devs and also why a torch before the first nightfall is a critical day one objective.
Welcome to Vintage Survival... err, Vintage Story where even the dirt wants to kill you. 😊