1) All but Ross County, Elgin and Cove. Edit: forgot New St Mirren Park. (Only Scottish ground I've been to and not seen Sons play at is Grant Street Park, Inverness.)
I've also seen Sons at Old Bayview, Annfield, Firs Park, Shielfield, New Kilbowie, Broomfield, Shawfield, Old Douglas Park. Edited to add : forgot Brockville. (Sadly I missed Cathkin - and Raydale.) And outwith Scotland, Park Hall Stadium, Oswestry.
2) All but Ross County, Elgin and Cove.
3) Boghead, first away was Hampden to see Queen's play the Sons in the 1960s.
4) Balmoor - this season.
5) After Boghead (natch,) Firs Park, followed by Glebe Park, then Cliftonhill - all nostalgia fests, football as it was and as it should be.
6) I don't have a least favourite.