I have been trying to downgrade from Big Sur to Sierra.I have 2015 early MacBook Air.Big Sur makes my comp slow that s why I am not pleased with its performance.I downloaded Sierra but couldn't start.I tried Command Alt Option R nd started recovery menu but it got stuck while setting up Sierra.I want to delete all in comp and want to set up Sierra.
Hi,
If you have TimeMachine back up, you can downgrade quite easily, though try to start up in Recovery mode(Shift+Option+Command +r) then reinstall macOS which is installed macOS that came with your Mac.
How to reinstall macOS - Apple Support
There is no downgrade.
If you have a backup from prior to the upgrade, it is possible to revert.
If you don’t have a backup, or if you have been modifying files and making changes since the upgrade, then reverting will involve data loss.
Erase, and re-install. Or erase, and restore your pre-upgrade backup.
downgrade from Big Sur to Sierra or High Sierra.
