Do you have to stay at the hotel ?

Only hotel guests are allowed to use the water park it is included in the rate

No, you don't have to stay at the hotel to use the water park. However, you must pay to use the water park. It is not free to use.

You have to stay at the hotel to use the water park. If a friend is staying you can also pay $50 for a pass at a 1:1 ratio I think (meaning one extra pass per guest). The 5+ person at the hotel also costs $50 per night. The rest of the activities I read are open to the public for a cost.

You can also purchase a pass if you know someone staying there.

If you want to use the water park, yes. They use a wristband system to check you in.

Yes.