Screen Time forgotten passcode

If using IOS 13.4 or newer.

Screen Time passcode reset

Another option.

You will need to restore the device to factory settings. Do not restore from a backup made when the Screen Time code was active.

Restore to Factory setting.      

Backup - Restore your device from an iCloud or iTunes backup.     

About the Screen Time passcode on managed devices - Apple Support

Screen Time passcode reset

Forgotten Restrictions Passcode Help

  •   iPad,iPod,iPod Touch Recovery Mode

  •   How to erase your iOS device & then set it up as a new device or restore it from backups

  •   About Restrictions (parental controls) on iPhone, iPad, and iPod touch - Apple Support

  •   Use parental controls on your iPhone, iPad, and iPod touch - Apple Support

You will need to restore your device as New to remove a Restrictions passcode. Go through the normal process to restore your device, but when you see the options to restore as New or from a backup, be sure to choose New. You can restore from a backup only if you have one from BEFORE you set the restrictions passcode.