alece, thank you very much for fast reply.

It is 3g.  I was thinking of jailbreaking it but there are so much information in google that I couldnot figure out what to do. 
Before jailbreaking it, I just have a basic questions

Do I need to know which IOS my phone has? 
Do I need to know the baseband version?
If yes, how can I find out these information? (because I cannot enter to the phone and itunes doesn't give any information)

Thanks again for the information.