Forgot restrictions passcode

You need to restore your device without using an iCloud or iTunes backup.

If you forget your Restrictions passcode, you'll need to erase your child's device, then set it up as a new device to remove the Restrictions passcode. Restoring your child's device using a backup won't remove the Restrictions passcode.

Read: How to use parental controls on your child's iPhone, iPad, and iPod touch - Apple Support

(or restore from a backup created before restrictions were enabled.) There's not a great chance this will be helpful, but if you only recently enabled restrictions, well, there you go.