Failed to update to iOS 8

What is the model number of your iPhone? Settings>General>About>Model.

You may have to scroll to see the entry for Model.

If you have an iPhone 4s, you should be able to update to iOS 8. If, on the

other hand, you have an iPhone 4, iOS 7.1.2 is the latest iOS version that

will install on your iPhone.

Identify your iPhone model - Apple Support

Pleas check the number at: Settings - General - About - Model = ???

The information you have presented, suggest that you have an iPhone 4.

Does your phone have Siri? Dictation?

That model is an iPhone 4, which can not be upgraded beyond 7.1.2.

That's an iPhone 4. Not a 4S. It's as up to date as it can get.

I am quite sure you are mistaken. You have an iPhone 4.

If you purchased it as a 4S, you've been ripped off.

You have an iPhone 4, not a 4s. iOS 7.1.2 is the latest version that will

install on an iPhone 4 - you are up to date for that iPhone.

If you want to use apps that require a later version of iiOS, you will have to

purchase a newer model iPhone.

You are perfectly welcome to reject reality and substitute your own, but it won't change the fact that you're wrong. That's a 4. Google it.

No idea what you're seeing in iTunes that says it's a 4s, but as far as the box is concerned, it's easy... that's not the box that goes with that phone. It's a 4.