>>iPad gave me “CAUTION ABOVE 12,000FT” WARNING and exploded.
That's NOT a warning from iPad. That's simply a reminder from ForeFlight about the 12,000 ft oxygen requirement (from FAR 135.89), and has nothing to do with the iPad's physical limitations.
That is NOT a limitation and exceeding it is not a warranty voiding event. That's just the tested range. Two very very different things.
Depends on the model. For older generation iPads, Apple did specify a maximum operating altitude (screenshot below):
However, all iPad models -- back to the original model introduced in 2010 -- have been shown to comply with FAA environmental condition standards (RTCA DO-160) -- which includes rapid decompression testing to 51,000 ft.