Sometimes when your desktop or your laptop gets stuck or unresponsive, you need to forcibly shut it down. Similarly, sometimes an app is running in your iPhone or iPad and due to some error it gets stuck and we call such an app ‘frozen app’. As a result your device stops responding as your home button stops working.
At such a time there’s no option but to force quit that app and for that you need to learn to force quit app on iPhone, iPad and iPod Touch.
How to Force Quit App on iPhone, How to Force Quit App on iPad, How to Force Quit App on iPod Touch (It’s the same on iPhone, iPad and iPod Touch)
Hold down the Power button at the top of the device until the “Slide to Power Off” message appears and then release the power button
Now hold the Home button at the base of the screen until the app forcibly quits, this can take several seconds
You’ll know you have successfully force quit as the app will close and you will be returned to your home screen and icons.
If the problem of stability issues persists you need to backup and then reset to factory defaults or restore to try and resolve the problems.