Can I go back to Windows 10 after I upgrade if I don't like Windows 11?
Within 10 Days of Installing Windows 11
After you have installed the Windows 11 upgrade, there is a 10-day period where you can move back to Windows 10 while keeping files and data that you brought along with you.
10+ Days After Installing Windows 11
After the 10 days, you will need to back up your data and do a "clean install" to move back to Windows 10.