Can I update iPhone 3 to iOS 9?

According to experts, this is just not possible technically. Released during a San Francisco keynote, iOS 8 is a new software which has many advantages. Firstly it predicts text using Quick Type. Secondly, it also has other features like a notification menu that is interactive and a whole slew of native photo editing tools. iOS 8 is already 1 year behind the latest iOS 9.3 that have a lot features like Night Shit Mode and low power mode.
Devices compatible with iOS 8 include iPhone 4S, 5, 5C, 5S and iPod Touch 5th generation. The following iPads are also compatible with iOS 8- iPad 2, iPad Air, iPad with Retina display, iPad Mini, iPad mini with retina display.
However, the following devices cannot work with iOS 8- First Gen iPad, iPhone 4 and earlier models (this includes iPhone 3) and quick access to favorite contacts with the double tap. While developers got their beta version before, users had to wait for the official release.
Features of iOS 8: An Overview
iOS 8 (though cannot be installed on iPhone 3) is a majorly enhanced and easy set of features along with what was previously present in iOS 7.
The most important addition to this iOS is the use of Apple Pay which is based on NFC technology. When at a counter, you can use your iPhone to pay the bills- this essentially revolves around the easy scan of credit cards using the camera in the iPhone.
Apps like Messenger and WhatsApp have received a boost because the regular messages have been modified in iOS 8. Located towards the top of the details page, there is contact information with buttons to make calls, lead on face time or look at the complete contact details of a person.
Messenger app now makes it easier to send group messages and browse through conversation attachments. In the new iOS 8, the new Messages app is also in the Details section. Rather than scrolling down over time to find a single photo, Details section ensures audio and video clips as well as photos and locations are stored in a single place.
There are also more ways to communicate on iOS 8 with keyboard modifications facilitating communication. Words and phrases which are unknown can be predicted so easily using the predictive power of QuickType. Third party keyboards also support native support tracing for Apple users switching to iOS 8. With Siri going hands free and a slew of new features added to iOS 8, this makes it the best choice for those using iPhones. Pity the iPhone 3 users cannot avail of this option.
If you want to get the newer iOS 9, it’s time to upgrade because the older model iDevices have too slow processor which will cause more errors and crashes.
Other iPhone Upgrade