iOS lockout for my son's phone

My wife and I use Android and Focus Time and similar apps work great. The key is that they have password lockout functionality, meaning I can set up the app to block Instagram etc after using 120 minutes per day, for example. From what I've seen, iOS doesn't allow for this functionality, or am I mistaken? ScreenZen is a great app, but I don't see a way to password lock the settings.