I think by sold out it means allocated to clubs, probably not the best indicator.

With 10 sections left and only 2 weeks to sell. I'd doubt the top tiers get opened. If it was a final if there was more than 2 points up for grabs then it would easily sell out with those kind of sales. But I can't see there being much of a last minute rush.

I have received two reserved tickets; would I be able to get into the unreserved areas? Or could I go in the reserve stand, get a stamp to exit and then move into the unreserved area?

No I tried this last year, they won't let you in the unreserved unless you have a unreserved ticket. The stamps for both are different colour.