Answers:

1. I don't know. :-) sorry

2. Here is a link to a youtube video that will help with jailbreaking. I did it on my 3GS 3.1.2 with no problems. http://www.youtube.com/watch?v=kCMkN2sP2KA

3. Yes

4. Yes


I'm not an expert, so input from others is appreciated. Hope this helps.