Interwoven consequences - completing one mission will affect other missions in that stage.
Early missions act as tutorial levels without interrupting the flow of the game.
Yes, except this time there won't be an extended dialogue tree. It's not an RPG after all. Depending on the final size of the dialogue script, we are going to try and record all dialogue as audio. The NPC's will be able to recognise the player's reputation, and respond to them accordingly. At the moment, the maximum for multiplayer is 36, and in single player there may be more, depending on the mission.