I want to try to speedrun reach height limit set seed pre 1.18 like kobra and Khalooody did, but i can't figure out which version i should use to get the set loot in the ruined portal chest. Can anyone help me with that?

Wow Thats impressive

Watch a lot of runs from the leaderboard. Also there is a video from a channel "Eazy Speezy" where a guy explains how he does a run. When you got all that knowledge try actually speedrunning! Install the LiveSplit, OBS (if you still dont have those). When you can see that you can do a whole run but with some amount of luck start recording it.