IPhone 4

The iPhone 4 was the first iPhone with squared edge and all glass and metal construction.

Common issues

 * Loss of cellular signal when holding the phone "wrong" by using the left hand causing the skin of the hand to make contact with the antenna and bridging the two metal pieces on the lower left of the phone. A potential solution is using a non conductive case.
 * The home button will stop working after common wear and tear. Unfortunately unlike the iPhone 5, the replacement of the home button is not easy and a common fix is to use Assistive Touch, an accessibility feature of Apple iOS. To enable it, open the Settings app, tap General, then Accessibility, then Touch and toggle Assistive Touch on. It makes a virtual home button onscreen and restores the home button's functions.

Back glass replacement
The back glass is easily replaceable by unscrewing the two P5 (Pentalobe) screws on the bottom of the phone (on both sides of the 30 pin connector) and pushing up to free it from the housing. No cables are attached to the back glass so you can freely pull it off.