You must reserve a ticket online and go through a tour. Thursdays are free and reservations can be made here: https://buffalobayou.org/visit/destination/the-cistern/
You have to do a tour. They close and lock the door In between the tours. The thing isn't that big. There's not much to explore other than the perimeter of the cistern.
Generally you walk with the group, but you can hang back if you want to take photos or enjoy the sight. But if you're asking if there's some kind of private tour/exploration, there isn't one that I'm aware of. They've also got yoga classes, photography sessions and interesting art installations periodically.
No, you have to go through the tour.
You can be your own tour guide 😎 but with a tour guide could be helpful and fun
Thanks! Your answer is awaiting moderation.