Also, why do some layers (e.g. essential graphics) don't show up on V2 track, but show up on V3? And if you move it to V4 it has some display issues (shows up, but wrong). How is this a stable new update?
yes you can open your project in an earlier version of premiere. it's one of the new features. You export as an xml from 2021 and you should be able to open it in 2020. check the documentation... I haven't done it, just read about it in the new features page.