When I'm trying buy a ticket it says that it will give access for 30 min, i need to pick a time from 9:00-9:30am etc. Can i stay longer than 30 min?

You can get a stamp and come and go all day

That is what I did, visited in the afternoon and came back for the sunset!

its valid for the same day. you can leave with a stamp and come back on the same day. you have to keep your ticket with you.

No you don't have a pecific time you can go whenever you want but done go late more the an hour from the time you selected it closes 6 pm