How do I reverse "Catalina" update?

Hello joleekar,

The only way to revert your Operating System after upgrading to macOS Catalina is by restoring from a Time Machine Backup. If you have a Time Machine backup, you can go through the steps of erasing the computer and restoring your data using Recovery (Command-R) or Internet Recovery Mode (Command-Option-R).

https://support.apple.com/en-us/HT203981

If you have a Time Machine backup you would boot into Recovery Mode, erase your drive and restore from a Time Machine backup.

https://www.imore.com/how-downgrade-macos