How to limit kids access to one app on iPhone and iPad?

Follow the instructions below to lock iPhone and iPad to the current running app. Useful during kids’ FaceTime so that accidental touches do not interfere with the call. The feature also allows the parent to set a timer so the length of, for example, playing games, can be limited.

For iOS 13, 14, https://www.macrumors.com/how-to/limit-kids-access-to-one-app-iphone-ipad/