IOS 5 - iPhone 4S how to change back to old version?

Ever since I changed my iPhone to the iOS 5 version I can't turn my push notifications on and I need to do that so I can use viber how do I change it back and if I can't now do I turn my notifications on it doesn't say on and off normally I could just slide it to on.
Has anyone else had the same problem as me?

Try and upgrading it to iOS 6? That could solve the problem.

It's a network issue. You have to take out the battery and put it back.
As simple as that.

Oh mine is kinda same problem I upgraded my iPhone and after that I don't have YouTube app anymore. Omg it sucks cuzz can't watch any video. Please I also need help. Answer mine below this question. What should I do?

Since you are asking in the Google section and not the Apple section, the right answer here is to toss that iPhone garbage away and buy a decent Android phone. Hint hint, Google makes Android software for phones just as Apple makes the iOS software for iPhones.