Answer to: Display is flickering with gray stripes when tilting it.Flickering/distortion on movement is a clear indication that your display cable needs to be replaced. Not an easy fix in all cases, especially considering a MacBook Air.
Answer to: Can a cdma be switched to GSMYou can't really do that. You'd need at the very least a new logic board and new antennas, which in the case of any iPhone that can be CDMA, is the external case. You're better off selling the phone and getting a CDMA iPhone for a similar amount of money as what you sold your GSM one for.