How can i upgrade iphone 4s to ios 8?

If you have an iPhone 4, you can not upgrade beyond 7.1.2

If you have an iPhone 4S, you can upgrade to 9.2.

You can't. An iPhone 4 isn't capable of running iOS 8, and iTunes won't allow it to be installed onto an iPhone 4S; if it's somehow force-installed, the device won't activate.

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tiagorocks wrote:

I have an iphone 4S and now I am confused: can I upload to 9.2 or not? And how to make it without using the normal upgrade IOS?

Yes. You can insstall 9.2. Niel erred in thinking you had an iPhone 4, not 4S

You simply update as always. Nothing new or different at all. Just update your iPhone and you will ahem the latest available software.

The reason people are bringing up an iPhone 4 is that, at the bottom of your first post, you indicate that you have an iPhone 4.

An iPhone 4S can be updated to iOS 9.2. Go to Settings>General>Software Update or connect the phone to iTunes and update it through iTunes.

BACK UP YOUR PHONE BEFORE YOU UPDATE. Please.