Step 3: Click Accessibility
Step 4: Click Guided Access
This will start the prank. Turn on guided access on a friends iDevice and enter a password you have to remember.
Step 5: Add the Pass Code
Step 6: Go to the App You Wanna Prank Them On.
I used minecraft pocket edition.
Step 7: Start Guided Access
Circle the parts on the screen that will be disabled. (Insert evil laugh here). Then start click done and they will be at your mercy. Sorry but I couldn't take a screenshot with this.