Apple has released final version software or firmware for iPhone and iPod touch. It’s called iOS 4.0. This iOS 4.0 is for iPhone 3G, iPhone 3GS and iPod touch 2G/3G.
Before releasing this iOS 4.0, Apple was released iPhone OS 4.0 Beta 4, Beta 3, Beta 2, and Beta.
The iOS 4 is supported on iPhone 3GS [...]