How do i downgrade to a previous version of the game? + How to update a bought server?

[Emma Bones]

so i'm playing on a public server, updated my game today without thinkingand now i can't log into the server because it's not updated, so i thought i'd play on my own server which i bought hosting for wile buying a game account and same issue. I wanted to know how can i update my own server and how to downgrade to a previous version, just in case. 

thanks in advance

 

[Thorfinn]

Welcome to the forums, @Emma Bones