Depends on where you live. I live in Michigan so Im pretty close to a distribution center thats in Pittsburgh. I'll usually see a 2 day wait for them to receive a game, and another 2-3 day wait to get a game back. IF its available.
I don't think you HAVE to, Its just they like you to have plenty of games in the Q so they can send another if one's not available. Im not the best example of that :P. I have only 1 game out right now because Im waiting on two games that have "low" or "very low" availability
No, I always tear the serated edge and throw away the part thats not the return envelope. Gamefly probably uses other information to determine that it was your game that you returned(different serial numbers etc.). That's how i've always done it.
When You're in your "My GameQ" you should see a section that says "Games I have out" In that section you should be able to see something that says "Upgrade to 2 games at a time!" and there is a geen "Upgrade" button that you can click on.
Hope that helped.