Let's see if I can help answer some of your questions.
1. You can purchase an AP on Disney's website. They will send you a voucher to redeem. You can also wait until you arrive and purchase an AP at any Guest Services before entering the parks. You do not have to have an AP in hand to actually book the AP discount, but you WILL need it when checking in...just in case they ask you for it when you check in. If you are wanting to book online using the passholder web page, then yes, you would have to have your Voucher for an AP or the actual AP to log in.
2. Yes, you can get the
DDP added on. However, as an AP holder you can purchase a TiW card for $75. This is good for up to 10 people. It gives you a 20% discount off of food and alcoholic beverages. This card is good for table service restaurants unless you're staying at a resort that does not have a table service restaurant...then it covers the counter service restaurant. This card has saved us a lot more money than the DDP and my older parents get so aggravated trying to figure out the DDP. Alot less hassle especially when the CM's aren't familiar with how the DDP works. As an example we went to Casey's corner on the DDP. My dad wanted a hot dog, coffee and a water. The CM kept insisting to dad he couldn't do this. Yes, you can. It would be charged as one CS for the hot dog and coffee and one snack credit for the water, but neither my dad or the CM could figure how to work this and both got very frustrated over it. LOL
3. The regular AP does not cover the water parks, but you could purchase the Premium AP which would include the water parks and more. If you are only planning on going to the water parks once it's not worth it to upgrade to the Premium.
4. I have been able to book up to 3 rooms per Adult AP. Other's have stated Disney has changed this rule to only being one room per AP, but I have never had that problem. I just recently (this month actually) booked two rooms with my AP discount.
5. The AP discounts that I have come across has been applied to all levels of a resort, however, I've never booked a CR TPV room level. I have been quoted the discount for that level of a room, but did not book it.
Hope this helps some!
