iOS 4.0.2 for iPhone and iPod Touch and iOS 3.2.2 for the iPad were released on August 11, 2010, to fix a pair of security vulnerabilities.
iOS 4.1 for the iPhone and iPod Touch was released on September 8, 2010; the update fixes some bugs reported by users, improves battery life and adds a new feature called Game Center, which allow gamers to multiplay, upload high scores and to unlock achievements (though, Apple removed Game Center from the iPhone 3G due to reports on slow performance) and adds initial support for the iPod Touch 4th Generation and the Apple TV 2G. iOS 4.1 also updated carrier settings which in the US was AT&T 8.0 and enabled toggling Check Spelling On/Off. iOS 4.1 also adds HDR photography, a feature that only the iPhone 4 is capable of using. TV Show Rentals are available on the iTunes US Store. iOS 4.1 also adds a new feature called Ping which is a social music network and discovery tool.
iOS 4.2 was released to developers on November 8, 2010. It was never released to the public as a Wi-Fi bug was found during the limited release. Apple then issued two more golden master releases. Finally, Apple released iOS 4.2.1 to the public.
iOS 4.2.1 was released on November 22, 2010 with support for all Apple A4 devices, 3rd-, and 2nd-generation devices, with the exclusion of the Apple TV. It brings initial support of iOS 4.x to iPad, plus AirPlay and AirPrint to all compatible devices. It also contains minor changes to the YouTube app and alters the multitasking animation. On iPad, the screen rotation lock button's functionality changes to mute, the same as it was originally planned. As a known major bug, this version seems to hinder the usage of the Camera Connection Kit on the iPad.