Downgrade Chrome OS

Disconnect all network connections on your Chromebook.

Open a terminal window by pressing ctrl+alt+T, or go to chrome-untrusted://crosh in a new tab.

Run command rollback on the terminal window, and press Y to confirm.

Check the output message to see if the operation succeeded. If not, you might have to bypass the admin lock before doing so.

Restart your device. Your device should be downgraded to the previous version.