Question About NRG

Planning to go to my first Texans game tomorrow! I know to park nearby and take the rail, but I had some other questions:

How strict are ushers? Was planning on buying nosebleeds and then heading down after some scouting. Will they just let me walk in without even checking if there’s a lot of empty space? Can I go early on, or should I wait until after halftime in case of latecomers?
What’s the water policy? I’ve read different accounts about empty plastic and reusable bottles being allowed, stands being obligated to give water cups for the fountains, etc. Not sure what is true.
Is the roof closed during games? Or do I need to go buy sunscreen?

Thanks very much for any answers!