Hoe to unlock and completely reset a iphone 4?

How do i unlock a iphone 4 and completely reset it like the apple account and stuff. I don't know the current apple account and password. The phone is my uncles old one (he has a new one now) and i just want to use it for apps and music and stuff.

You have to get your uncle to log into it, remove the password/code and then de-register it from his account using his iTunes. Otherwise it's probably flag as stolen!

If it's running iOS 7 then you will need the password and username or there's no way in