Hey Kant, I think you've just demonstrated why the a1,a2 etc are a good idea. I believe you are correct, and we didn't see the a2 until MY85. If memory serves, DCC is also correct, in europe the a2's were released long before we saw them in Canada. I had, long ago, an 84 a1 jetta.
Back on topic, the mk3 seats will fit in a mk2, with modifications to the seat brackets, or more nicely by swapping the metal seat base from a 90-92 mk2 seat into the mk3 seat. There are several posts about this on the vortex, and IIRC, at least one on this forum as well.