This video will help you fully activate your iPhone 4 and no service problem might also get fixed if your iPhone is NOT carrier locked!
You will also learn how to Jailbreak Untethered using PANGU Jailbreak for iOS 7.1.2
You can log in to your own account and iTunes on the phone and install any application you want. You can use iTunes for backups, music sync, and so on.
I decided to update the video I made back in May 2015 as I wanted a greater sound/image quality. Enjoy 1080p HD.