Since upgrading to iOS 9.1 my iPad mini does not work I upgraded my iPad mini this morning to iOS 9.1. I have the first gen iPad mini. 
Since iOS 9 I have been experiencing app crashes and my iPad getting stuck a lot, but since upgrading to iOS 9.1 my problems have upgraded to my iPad just going black while I'm doing something on it. When I press the home screen button it comes back on for a second before going back again. As if it's constantly locking itself. Tried turning off and on again, didn't work.

What steps should I do to determine if the hardware just broke or if I can fix it with software?
One of the things that they always tell you to try is to do either do a full backup to iTunes or iCloud and doing a full iPad reset &amp; restore. (Settings -> General -> Reset -> Reset All etc)

But obviously be careful about what apps you have and whether there is data that won't get backed up. There is no 'revert'.

Eliminating the possibility of a software problem is easier for you than determining a hardware problem. If you still have the problem after a full restore...

Do you have warranty?