The unplayable game is "101-in-1 Megamix", it costs 9,99 in the european PSN store and can currently not be bought/downloaded/installed/rated.

If you buy this game with your european PSN account, and then try to play it at your imported asian PS Vita device, you will be unable to properly play the game, since the button assign of the X/O button prevent actually playing the game.

At asian Sony devices the X button is used to decline/cancel, and the O button is used to confirm/access things.

So basically the other way around of how the EU/NA devices behave (X for confirmation and O for canceling stuff).

The European Sony Customer support and the Germany Sony Customer support were so kind to tell me to "suck it up" as Ive requested that they either: a) Fix the game, so it can be played; or b) refund me my money (not as a chargeback or in cash, but as PSN wallet), so I can buy another game for the money.

I think this is not a nice way to deal with your customers. Adding the ability to manually decide if you want to use the X or the O button for confirmation, and the other one for canceling events should be available in the settings application of the retail PS Vita.