go to https://www.oneplus.in/support/softwareupgrade choose package which is suitable for your phone download it save and go to local update and...
yes..you can
Already format twice .. but again getting stuck issue in many apps. RAM always free 3.1GB but don't know why this happened..
After update 9.0.5 Phone gonna too slow. heating problem less but Always Stuck on application.. please add video call over VoLTE without using any...