I have brought iPad Air cellular with 32GB in December 2013. It was best when I was using iOS 7.1.2. When I have updated to 8.1.2 it got hung. After resetting all it started working.
Later again it got hung and unable to boot. With lot of trouble it got updated to iOS 8.3
Later again after some time it started giving same trouble and again i got updated to iOS 8.4 after trying a lot.
And now after trying a lot I am unable to restore or boot it.
iPad Air, iOS 8.4, Serial - DLXLP3ECF4YJ