The restricting apps would have been for all of those device types instead of by age to make it simpler and less intrusive.
Regulating smartphones is overkill but honestly would make it a lot simpler and be less invasive.

You could also regulate smartphone sales. Only dumb phones until you hit 18 or so. It wouldn’t keep them off message boards but it could help with social media. Maybe restrict social apps from working on tablets to close a loophole.

As what happened?