1. Yes
2. Inflexible. But Air + , which you pay extra for, is flexible. Within reason, you can pick your flights. I have my flights in mind, and a backup, before I call.
3. Yes, but as others have said, the higher (more expensive) cabins get first dibs at excursions and dinner reservations. If you "miss out", you can *usually* book what you want once you are on board.