Can I restore my Iphone then restore it with a previous back up?

Can I restore my Iphone then restore it with a previous back up?

Added (1). I have an Iphone 5c and IOS 8.0.2 and I got the swiftkey app and deleted my english keyboard. ANd my passcode was "a" with a symbol on top. And I can't acess my phone at all… I can't go into recovery mode So I can I restore my iphone then use a previous backup?

Added (2). so i'm locked out of my iphone

You can downgrade your phone but if you will keep on changing your OS your iphone will start draining soon.