Backup iPhone 5s in Lost Mode?

I recently bought a iPhone 5s which turned up being in lost mode, I was told there isn't a way to reset the phone but what if I were to use my backup from my iPhone 6 on the locked 5s, would it work? And if not is there any software I can use to bypass the lost mode?

You can't do anything without the owners password. That means you can't wipe it or reinstall anything on it, and can't turn off find my iphone either.