I have a 3g iphone that is jailbreak with 2.1firmware. What will happen if i update it to 2.2 via itune? will my phone brick? will my phone stay jail broken? plz help
No. You can jailbreak it if you want to. It should be fine. The only worry about 2.2 was if you wanted to unlock your phone, but that is now a non-issue.
Next time search first, because there are about a dozen threads just like this with the same answers. Not to mention this would belong in the iPhone hacks section.