Restrictions passcode

See the following from https://support.apple.com/en-us/HT201304

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.

If you have a backup made before you set up your restrictions passcode, you can restore from that backup.

Shouldn't be this case, you have two options:

Cohabit with the restrictions

or

Restore your iphone to factory settings (without then restoring it from a backup, 'cause the restrictions passcode will come back again). You'll loose all your data.

Regards

Giulio