First and foremost, I want to know what kind of a movie theater you're going to that has reserved seating??? The only things I've had to reserve seating for have been sports venues and theater productions (like Phantom) I usually go to Cinemark theaters, and have a pretty decent time. I highly suggest getting there early. When I saw The Force Awakens last year, 3 days after it premiered, I didn't get there until a few minutes before the movie started, and ended up in the 3rd row. "Never again!" I said, not knowing that I would be in the first row when I saw Deadpool in February.
I'm planning on going Friday or Saturday (at a local Cinemark), and buying my tickets in advance (once I figure out my dad's schedule, since he'll want to go). We'll probably get there at least 15 minutes early (though I think the latest would be 20 minutes lol). I live in a university town, and most of the students should be gone by Saturday afternoon, so there shouldn't be a huge wait at the theater (though again, I have learned my lesson after TFA and Deadpool). I think it all depends on what theater you go to, and what crowds are usually like for opening day movies. I fully expect theaters to have several screens reserved for Rogue One, so it should be easier to pick a time that works best for you.
Looking back on your other posts, I think you should be okay going into Rogue One without any prior Star Wars knowledge (I think). Sort of like how Fantastic Beasts and Where to Find Them can stand on it's own without Harry Potter, Rogue One should be able to stand on it's own. Before you ask- the sequel to Rogue One is called Star Wars Episode IV: A New Hope. It came out in 1977
This is probably going to be the only movie with these characters (because I fully expect 75% of them to die before the end).
In terms of the watching order (idk if you've started yet), I'd simply just watched IV, V, VI, and VII. If you want, check out the prequels for Young!Natalie Portman, Liam Neeson & Ewan McGregor doing a pretty decent job with what they're handed, Jar Jar Binks- the worst Star Wars character ever, and Darth Maul- one of the coolest villains designed who unfortunately was not given a lot to do. I don't remember anything from the prequels being mentioned in The Force Awakens (episode VII), so you probably could be okay skipping them.
(This turned out to be a lot longer than I expected, please let me know if you have questions)