i just use to study on duolingo and zoom. i don’t play game
should i update my ipad air 4 to ipados 15 public beta?
No.
Unless you have specific reasons for using Betas, you should stick to release versions.
Betas are less reliable, consume more resourses, have poorer battery life, and some apps may have issues.
Update to the release version of iPadOS 15, when that becomes available.