Trying to upgrade my dads 5 to his 6+ I got him. the 5 is on 8.1 and 6+ came with 8.2 so icould cannot restore from his backup. Trying iTunes now but I keep getting an invalid signature error so im redownloading ITunes. Anyone have any suggestions how I can get either 8.2 on the 5, or downgrade the 6+ to 8.1 so I can get his contacts and info on it.