Update to iOS 8 will not work for 4s Ok, this is the weirdest thing ever.

So I have a 4s and i can't update it past 7.1.2. I tried everything but it won't work. It is said that the iphone 4s can update to ios 8 (via apple support) but it won't work. On this site it says that it can't but that's not possible cause my friend has a 4s too and she's already at like 9.3. There might be a bug in the software that causes that for me but the issue is growing so i am just puzzled and I am sad cause i want free starbucks but i can't get it. ( starbucks rewards needs 8 or higher.)
It’s almost certain your device is either:


failing and in need of hardware repair
not 4s and actually 4


You can verify the model number or call Apple support to be sure you have a 4s and then see about arranging service if restore attempts fail repeatedly.