I'll take the easy ones. lol To be best of my research and experience at least.
6. Never, I have a 20+ year old fig tree in my neighborhood and there are many members here who post pictures of their/their family member's trees that are even older.
7. Yes, done this myself, zero problems.
9. There are different flavors of figs, berry, honey, ect. Usually people that don't want 40 trees will get one of each flavor, and others will get multiple of each flavor and weed it down to just the ones they like.
10. This is VERY common, it would be very hard to prove that this 1 year+ old tree was the little one you bought from them, if you still have the receipt. They could also have been fooled by the person they got it from and sold it falsely to you accidentally, this is what happens a lot with nursery's that don't do their own cuttings/grafting as well as amateurs who don't know better.