Diamond. Can you still buy mk2 sunroof seals from vag do you know?
No idea, don't have a sunroof

Bear in mind that VW seem to be sticking to the 15 year agreement pretty firmly, so any car-specific parts are going to be dropping off the availability list now. Lots of Rallye stuff is now obsolete, for example. Anything used elsewhere in the VW stable will potentially be available for years - lots of G2 hardware was used on the Toledo up until 1998.