Atlantis Dubai

I am considering to spend 1 night in the Atlantis hotel (because of its special offer), and i would like to ask you some questions:
1) is there a possibility to early checkin ? Because officialy the check-in begin at 14.00 and the check-out is till 12.00 next day. Since i would like to spend whole day there and enjoy all attractions, i would like to make check-in as soon as possible...
2) if i will not decide for booking the hotel, i would buy a day ticket to the water park "Aquaventure" - do you think its necessary to book it in advance, or just at the arrive there?
Can i see the Atlantis hotel inside with this one day ticket?
Thanks for every advice

Aquaventure - yes you can get a one day ticket on arrival no need to book in advance, if you buy The Entertainer you will get 3 x buy one get one free tickets for Aquaventure. Most of Atlantis (shops, and Aquarium is open to public for free) but hotel lobby, pools and grounds are not open to general public.
Early check in will most likely depend on if rooms are full the night before or not.

Like he said above it depends if the room are ready,but I have gotten into many hotels very early and have never had a problem with that.They will also keep your bags for you until your room is ready so have some clothes you want to wear around until the room is ready at the top of your bag then go change and let them hold your bags.