Can't answer all your questions with certainty, but yes, the 8500 mobo should work fine in that 7200.

AFAIK the 7200 PSU and mobo connectors (to power, SCSI, floppy, etc.) are all identical to the 7300-7500-7600 series. And I know from personal experience that one can put 8500-8600 mobos into the 7x00 machines.

So you should be good to go. As to whether the result counts as an 8200, that's more of a philosophical question.