Reset restriction passwords
How do I reset my screen time restrictions password?
Question marked as
You will have to forcibly erase the device if you can't remember the screen time/restrictions passcode.
You can do so by forcing the phone into recovery mode and restoring iOS using iTunes or by using Find My iPhone.
After doing so, you will have to set it up as a new device.
Do NOT restore a backup made after the passcode was set. That's part of the backup. If you restore from a backup, you'll end up right back where you started.