Time in settings. Limits apps from being installed/deleted and requires a password for changing any settings.

Word of advice, don’t forget the password. It doesn’t reset like the phone’s password. My kid would do things like see our fingerprints on the phone after unlocking or give it to us near mirrors or windows with the intention of figuring out the password. One time it took over 100 attempts to try to remember the password. Otoh, his fault for his craftiness that caused us to change passwords so often.