I'll do the easy question. Via bidding on PRICELINE you have to be willing to accept any hotel within the zone boundaries of the zone or zones you are bidding, at the star level you are bidding or higher (an upgrade). You can't count on your bidding to get you an specific hotel. Besides the hotels members have posted as receiving, it is always possible to get a completely different one (speaking from several experiences). Via Priceline Express, with the help of the board experts identification, you have a good chance of getting a specific hotel, but even that isn't for sure (again, speaking from experience). Some of the identifications are more confident than others, but none are 100% guarantees.
I'm a member, not a board official. Just thought I'd help a bit. Romelle