What are those 2 parts on my tab's circuit board?

The whole piece of circuitry near the top seems to be the logic board for your tablet. This contains the flash memory and (what seems to be) the WiFi receiver and transmitter on it. If the highlighted chip which you think is the CPU is actually the flash memory chip, that would make sense with it overheating when you're making a backup. There's nothing on the underside of the board itself which could create heat (there could be something touching it on the other side, however if it's heating up the board to 91 degrees it would have to be very hot), just to note.

I don't believe the CPU, or GPU in fact, would be located on the logic board. Replacement ones can be bought (replacement logic boards, that is), however they aren't cheap and it might be better to get a new tablet. Also, if you do purchase a replacement one, it will have a different memory chip, and therefore will not contain any of the original data or files which the old one had. If it's getting as high as 91 degrees, I'd be thinking something's beginning to go wrong.