how can i update my IPhone 3G

Search!!!!!

http://lmgtfy.com/?q=how+to+update+iphone

If you iPhone 3G is at iOS 4.2.1 that is the end of the road .

The 3G does not support above that level

hey, i noticed all apps in itunes requires 4.3 so does that mean i can't use apps anymore?

I doubt that all apps require ios 4.3

An iphone 3g cannot use any apps that require ios 4.3 or higher.

It can use apps that require ios 4.2.1 or lower