what's the point of adding Vitamin B1 in Agar for germination of Orchid seeds?
 

how does that work when Vitamin B1 are heat sensitize? would it be pointless to add it in.

B1 is an easy-to-absorb source of carbon and a bit of nitrogen. Whether any of it is still available after autoclaving, I cannot say.

Maybe. If you don't add it, and you still get reasonably good success, then leave it out. Otherwise, if adding it still provides the plant with something beneficial - even if not what somebody originally set out to be, then could always just leave it in too.