Can I take photos? What about flash?

You can do whatever you want with your camera, as long as you’re doing it from your seat. If you try to get into the aisles or stomp on people to get photos, the ushers will ask you to sit down, or maybe even ask you to leave if you continue to misbehave. Also, this assumes your camera is a regular consumer camera. If you have professional video equipment, such as for making TV programs or documentaries, that could be a problem.