Hiya! Most of this is "it's up to you" but here are some answers anyway!
1. Usually people play this as close to our world, except with playing card-based demon summoning in it.
2. Usually it's an invented character, though you could always play someone who shares your name and background, if you wish. The downside there is that you may find yourself doing stuff like putting hexes on real people, which we wouldn't really advise doing.
3. Hmmm. That's kind of an in character decision I guess? I'm not sure what Jax would say about that. What I will point out is that if you keep the extra Jokers, you'll have a greater chance of being magically attacked and/or contacted by another deck runner, because that's what those cards do.
4. It's entirely open-ended. Wreck This Deck is the kind of game you can play as a short, as a lengthy campaign or dip into when you feel like it. There's nothing in the game that gets in the way of any of these approaches.
5. You decide what each card draw and prompt means. You could end up deciding that something has gone so badly wrong that your character quits as a deck runner, or dies. Similarly you might decide that you "lost" an individual challenge in your deck runner's life. But that is up to you, to interpret what the cards are telling you about your story.
6. The only thing you have to perform is the annotating of the cards and writing your journal, since the game won't really work without this. Some people like to perform in character rituals or other physical actions associated with annotating the cards. (For instance, we have a Wreck This Deck card in our freezer at the moment.) You can go beyond that, but there aren't any rules in the game for doing so and all the usual warnings about emotional bleed and so forth in relation to live action roleplaying apply. In short: if you have never Larped before, it might be an idea to read around it a bit before diving in, as this could be quite an intense experience!
