Stay there as long as you want, you are free to leave whenever. Check out the phone app or a normal map to see everything there is to do.
It takes a good 7 hrs to do the hole park if you are adventurous and walk realy fast between exhibits but the passes and parking are good all day long you can come and go if you like. With the exception of fast passes those are one time only
No, if you only want to do the rides once each, you can finish well before the park closes. If you add ahows and characters in, you will need the while day.
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