Can I buy tickets when I arrive at the park? can i stay until the park closes?

You can buy tickets at the gate *but* there is a limited number sold if not already sold out from reservations.

YES and Yes

Buy tickets before because you have to make a reservation to go

Only online ticket sales right now amd you must make a reservation. Once in you can stay till close

You have to make a reservation online right now to come to the park. You can stay until the park closes once you are inside.