You can pin an application's screen to keep it in view until you unpin it. For example, you can pin an app and hand your phone to a friend. With the screen pinned, your friend can use only that application. Lets start open Setting and tap on Security. In Security tap on Screen pinning. Now enable the the Screen pinning, second option is your choice if enabled after you unpin the application screen your Android devise will auto lock. Open the Application you want, tab on recent application button ▀ and then two menu dots in Android 11. From the drop down menu tap and Pin. Application will be pinned on the screen and 3 navigation buttons (back ◄, home ●, recent ▀) will not affect. If you want to unpin the application screen from Android 11 just touch and hold back ◄ and recent ▀ buttons at the bottom of the screen.