IPhone 7.1 update must connect to iTunes?

I have an iPhone 5. Recently, I tried to update it to the 7.1.2 update. When I started updating it, it turned off and said I needed to connect to iTunes. I did as said, did a hard reset, and everything seemed to be going correctly. But afterwards, it did the same thing, except now it just needs to factory reset. I've been plugging my phone into my computer, and it recognizes sometimes. But when I put it into reset mode or whatever, it says it isn't recognized.

I do not have the original Apple charger that came with the phone. The charger worked fine before the update thing, so I know it is NOT the charger.

To do updates on an iPhone it NEEDS to be connected to the Wi-Fi, not data.

First of all, make sure the basics are covered. Update Windows, update iTunes and make sure your iPhone is running the latest firmware. These steps may or may not fix the problem, but they do at least eliminate these variables. See also: How to update to iOS 7

It sounds ridiculous, but also restart your iPhone and PC. Many people leave their computer in sleep mode for weeks or months on end and until you restart it, updates may not be installed or configured. To restart your iPhone, hold down the sleep/wake button until a red slider appears: slide it to power off your phone. Hold down the same button for a couple of seconds to power it back on.

Finally, connect your phone using the original Apple USB cable and don't connect it via a USB hub: try one of the USB ports on the back of your PC or any on your laptop.

Anecdotally, we've found that unplugging and plugging in an iPhone 5c two or three times is necessary to get it to show up in File Explorer.