Here's a question for you and the OP, were these iDevices jailbroken?
Try these steps to successfully restore your iPhone:
Mac Users:
- Open Terminal (Open Finder > Applications > Utilities > Terminal)
- Type in: sudo nano /etc/hosts
- Type in your password and press the return key.
- Your hosts file should load.
- Put a "#" in front of any entry with gs.apple.com
- Control + O then press Enter. (This saves the file)
- Close Terminal
- Start iTunes.
Windows users:
- Close iTunes.
- Press Start button.
- Navigate to Applications > Accessories.
- Right click on Notepad and select "Run as Administrator".
- Once notepad opens, select File > Open
- Navigate to C:\Windows\system32\drivers\etc
- Select the hosts file. (If no files are shown, change the filter to "All Files")
- Add a "#" in front of any entry with gs.apple.com
- Save the file.
- Exit Notepad.
- Start iTunes and try again.
Here is the source where I got this information from:
How to fix iTunes error: "The iPhone "iPhone" could not be restored. This device isn't eligable for the requested build."