How to downgrade to Big Sur

You can downgrade by restoring to a Time Machine backup that you made, or by reinstalling the version of macOS that your Mac came with, and then upgrading back up to Big Sur. How to reinstall macOS – Apple Support (UK)

“Other macOS installation options

When you install macOS from Recovery, you get the current version of the most recently installed macOS, with some exceptions:

• On an Intel-based Mac, if you use Shift-Option-Command-R during startup, you'll be offered the macOS that came with your Mac, or the closest version still available.”

To add but this is a Very Drastic Measure. and should not be entered into lightly

It will only work on Intel based Apple Computers

ALL DATA will be lost and not recovery - period

To perform this action will require booting from a Bootable Installer. 

This will have to be performed from a Qualifying Computer to run the version of macOS to be made on the Bootable Installer. Example : Bootable Installer of Big Sur would have to be done on a computer that Qualifies to run Big Sur.

Once that is done read on for preparing the Destination computer 

>> Only works on Intel Based Apple Computers.

Extra Special Notation regarding the Touch ID equipped Apple Computer.

About Startup Security Utility and Must Enable from Recovery Mode the ability to boot from External Drive Before Attempting 

1 - Shutdown computer and disconnect all external drive Except the newly created Bootable Installer.

2- Restart and immediately hold the OPTION key until the Startup Manager appears and choose the USB Drive. 

3 - It will present options >> Disk Utilities >> View >> View ALL attached Drives. 

4 - Choose the Upper Most Drive ( not the volumes indented and list below ).

5 - The drive normally is called Apple Media or Apple SSD - that is the drive to Erase and format as APFS with the GUID Partition Map.

6 - Once that is done >> backup out of Disk Utilities and choose install macOS. 

7 - Follow the prompts and it may automatically reboot several time. 

8 - Upon a final reboot - Setup Assist will present with the newer version of macOS.

If yours came with Monterey, you cannot. Macs cannot boot from any OS older than what they came with originally.

Otherwise, follow previous suggestions.