Can you use a screen protector on a touch screen cell phone?

Yes. Your touch screen should still work fine. If you find a protector that's specifically made for your phone, i would buy that because you don't have to cut the protector to the size.

Do some simple research, go to amazon and you'll obviously see something like an iphone as screen protectors available, You're not very resourceful are you? So yes. You can.

Yes. As a matter of fact, they recommend you use one to prevent scratches.