This article explains how to "lock" an app on an iPad so that a user cannot close the app.
How to prevent children from leaving an app on the iPhone?
Guided Access is one of the accessibility features of the iPad. It keeps the iPad in a single app. You have to turn on the feature before you can activate it. Here's how:
Tap the Settings icon on the iPad home screen.
Tap Accessibility in the sidebar on iPad 13 and later, or tap General in the sidebar and then tap Accessibility in iOS 12 or iOS 11.
