iOS is the name given to the software on the iPhone, iPad, and iPod Touch.
Note that the Apple TV's software is also known as iOS, but it's version numbers are not in sync with versions of the other devices and the UI is completely different from other iOS devices.
iPhone, iPod touch (only the touch), iPad, and iPad 2.
The iOS on iPhone is the iPhone Operating System. Your iPhone runs on iOS. iOS is much like what Microsoft Windows, Linux, etc. are.
Sadly, no. The latest version of the 3rd iPhone (iPhone 3GS) is iOS 6.1.5.
iOS 5 will be compatible with iPhone 3GS as well as iPhone 4.
The current latest iOS version on the iPhone 4S is iOS 6.1.3 considering iOS 6.1.4 is for the iPhone 5 only. iOS 7 will be available for the iPhone 4S this fall.
Yes, you can run iOS 7 on the iPhone 4.
At the moment iphone 6 runs ios 8.1.3
The iPhone 5 will run iOS 6 or iOS 7.
The iPhone 4 can only support from iOS 4.0 to iOS 7.1.2. There is no way to get any higher iOS Firmware due to the older hardware that is built into the iPhone 4.
iOS stands for iPhone OS. When the iPhone Was first released, iOS was called iPhone OS 1.x.x. Today, on iOS 8, made people so mad bc iOS is a locked system meaning "un customizable "
The iPhone 4 can currently run up to the latest version: iOS 7.1.
Since ios 7 is designed for the iphone 5, it will probably make the iphone 4 slower.
This was created to add support for the Verizon iPhone. No device uses it except the Verizon iPhone 4, as the same feature was added to iOS 5, and the iPhone 4S included iOS 5. It is essentially iOS 4.2.3 for Verizon.
Yes you can, but expect some iOS functionalities that are on, say the iPhone 5S won't carry over to the iPhone 4.