No.
The release in December is likely to contain core elements of the game such as crafting, building and modding. That is where they are focussing their efforts at the moment. Obviously we will know what has and hasn’t made it in to December nearer the time, but these things will end up in the game at some point. Whether multiplayer is introduced before the September 2014 release or after, again, we couldn’t tell you.
Right now we don’t know. It’s something that as the time gets closer I’m sure we will have a clearer picture of, but right now we couldn’t tell you. Obviously there is the difference in multiplayer modes, between the asynchronous PvP mode, and the co-op mode, I assume you’re talking about the co-op mode.
I would hazard a guess that they will try and make it as easy and accessible as possible, just because, why wouldn’t you? But it’s just one of those things we’ll have to wait and see!