How to downgrade back to Catalina?

Greetings everyone,

A few days ago I downloaded Big Sur to give it a try. As it is still in Beta it is really buggy at some points and I could not work on my art works, that is why I decided to go back to Catalina and wait until Big Sur will release.

I used Option+Command+R to get in the recovery mode for Catalina version. I agreed to terms and when I needed to choose a disc - I could not do it because my disc was locked. How do I unlock that disc?
The setup assistant should automatically unlock your volume by asking for your password.

You don't want to do that though, as you wan to erase the entire partition and then reinstall Catalina.

To erase the drive you do not need to unlock the drive, just click Macintosh HD and then hit erase. You will be asked to erase all volume groups, be sure to do that. Then you can install catalina.
I think I have done that but it didn't install Catalina for me it installed me macOS Beta something.
How to downgrade back to Catalina?
 
 
Q