The Screen pin feature allows you to set just a single app that can be used until you deactivate the feature. This is helpful when allowing kids to use your device.
Set a secure unlock sequence (Knock Code, pattern, PIN, or password) in the Lock screen settings.
Enable the Screen pin switch and the Pin with screen lock setting in the Security menu.
Open the app you want used exclusively.
Tap the Recent Apps Button and swipe upward on the open apps list. The Screen pin is displayed on your most recent app.
If the app you want to pin isn't at the front of the open apps list, tap it to bring it to the front, then repeat step 1.
Tap the Screen pin icon on the app, then tap YES.
Touch and hold the Back Button and Recent Apps Button at the same time.
Enter your unlock sequence.