Yes.
You can install iOS 7 on your iPhone 4.
If at home in Wi-Fi, you can do so now in Setting>General>Software Update.
Yes, you can run iOS 7 on the iPhone 4.
Since ios 7 is designed for the iphone 5, it will probably make the iphone 4 slower.
Yes you can, but expect some iOS functionalities that are on, say the iPhone 5S won't carry over to the iPhone 4.
Sadly, no. The latest version of the 3rd iPhone (iPhone 3GS) is iOS 6.1.5.
The iPhone 5 will run iOS 6 or iOS 7.
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.
If you have an iOS 7 compatible device, go into Settings>General>Software Update.If your device isn't listed here, it means you can't get the update.The following devices support iOS 7:iPhone 4iPhone 4SiPhone 5iPod Touch (5th Generation)iPad 2iPad 3 - "new iPad"iPad 4 - "iPad with Retina display"iPad Mini
Now assuming you mean iOS 7, the iPhone 4, 4S and 5 will get it along with the two new iPhones coming out which are the iPhone 5C and 5S.
Ios 7 is the latest ios. Ios 7 is available on the fifth generation iPods, recent iPads and iPhones 4 and 5.
I doubt if you could ! Normally, you're only able to upgrade hardware and software to a newer version. That would be like swapping your current car for an older model.
No
Yes. The following devices will be able to legally receive the iOS 7 update in Fall 2013:iPhone 5iPhone 4SiPhone 4iPad with retina display (4th gen)new iPad (3rd gen)iPad 2iPad miniiPod Touch (5th generation)*all iOS devices released in Fall 2013 should be preinstalled with iOS 7.