1) There isn't any actual role-playing per se. Or well, at all. You can choose what weapon set you want, and what types of units are in your "squad" as for backstory, well, they've got some holotapes that tell a little bit about like, nothing really, just about the initial invasion in some sense, but really it's like you're dropped into this simulation with the assumption that you know that you're at war and that you're supposed to be doing these objectives that they tell you. As far as choices, like, nothing really more than what I've already stated, weapons and squad.
2) Not at all really. Like, they create the illusion that you can control units, but really you get like, four guys that follow you and your tactical descisions are either "stay here" or "let's attack"
3) I mean, I found the basis of the entire thing completely conveluted. Like, the reason for you doing the simulation. There isn't really a story when you're actually in the simulation.
4) I actually had a lot of fun. Like, it's not so much an RPG, and I don't think they were trying to make it one. It really seems like a typical first person shooting game I guess. I don't know, I liked the atmosphere and the idea of being a part of a battle and all of that. But I mean, I'm sure a lot of people wouldn't like it.