restrictions Passcode

You’ll have to restore your device using iTunes, which erases all data.

connect your iPhone to your computer, open iTunes and select Restore iPhone.

you can’t restore from a backup unless you have one made before the restrictions code was set.

if you have forgotten the Screen Time Passcode use this link If you forgot your Screen Time passcode - Apple Support

You cannot restore from the backup, because the backup contains the password. It will just put it right back on the iPhone and you will be right back where you started.