None of these helped me, but I did find the answer.
My iPhone (4S) was deactivated and couldn't connect to WiFi, and Find My iPhone had been turned on. I needed to wipe it in order to return it to Verizon, but couldn't Erase from the phone because of Find My iPhone requires an internet connection to erase.
The solution was to boot the iPhone into DFU mode.
DFU (Device Firmware Upgrade) mode is not the same as restore mode. DFU mode bypasses the current OS installed and allows you to upgrade or downgrade your OS. If you are getting errors trying to restore in iTunes, DFU mode is very likely for you.
DFU mode is not recovery mode. Recovery mode has a picture that says connect to iTunes. In DFU mode, the iPhone screen backlight is not even on and the display is blank. If you have anything on your display you are not in DFU mode.
This is how to achieve DFU mode. You can do it on every phone:
- Attach the phone to the pc
- Turn the phone off
- Press and hold power. Keep holding power. As soon as you see display on the screen of any sort press and hold home.
- Hold power and home together for *exactly* 10 seconds
- Release power but keep holding home until the pc beeps as a USB device is recognized.
- At no point will the display come on. Now your restore should work.
iTunes should detect your iPhone in DFU mode, and it will ask if you would like to reset it. If you want, you can make a backup of your iPhone's data before doing this. If not necessary, then just go ahead and reset your iPhone. Reset in this case means ERASE EVERYTHING to return to factory default.
4. Wait for a while, it can take up to and hour to reset. The computer downloads the latest iOS and then deploys it on the phone. When done, your iPhone should turn on, clean from all it's data.
Sources: https://answers.yahoo.com/question/index?qid=20131119125513AAtRloc
http://thebigboss.org/guides-iphone-ipod-ipad/dfu-mode