we can use the water park without use the hotel ?

Yes, but it's going to cost you quite a bit. 50-85 per person

You can use the water park without the hotel, but it's cheaper to go the hotel way.

You can buy a day pass ($50)but they only sell so many per day. Might be cheaper to get the room ($250) if you are going in a group of 4-6. You can swim around 1pm day of check-in and the next day even after you check out at 11am.

No, you can not