1) Not always. Some games are random babble and as such, allow you to really do anything you want (as long as you read the rules, and follow them), while others usually named with a 'RP' in the title, require you to have a character and to follow the rules to the letter.
2) Assuming the game in question is an RP, the person who started the thread countinues the story while you choose where the story goes.
3) No, but you may not get a response.
4) The forums work exactly the same as the regular forum
5) PM me, I have a whole post about that.
6) I'd suggest pale ale, not wine.