Starting a Game ahead of time
I don't know of any time limits requiring you to begin recruiting players within a certain time, but I've also never created a game from the ground up so I've never worried about that.
As far as changing names/tags on a game, yes, you can do that. There are some people out there who, rather than have deleted games show up when people search for information about them as a GM, will instead recycle their games...delete all the old information, empty the roster for the game, change the name and/or system, etc, and start all over from the very beginning. It's not the norm, but to the best of my knowledge, there's no policy against it at all.
If you set your game up TOO early/leave it sitting unpopulated for too long, it may get bumped into the equivalent of RPOL's recycling bin, but even then, you have time between then and when the game is officially deleted to bring it back to 'active' status.