I've been having issues updating my cousin's old iPad 2 WiFi (MC979ZP) from 4.3.5 to 9.0.2. I keep having Error 9 whether I use DFU or any other method. Apart from that, Apple has also stopped signing all versions of Firmware prior to 9.0.2, therefore any older firmware is unusable (Error 3194 without fix even using System32). I was also trying firmware 8.4.1 and older firmware.
By the way, I've tried many different original cables and many different computers, both Mac and Windows, including the garbage bin.
According to Apple's HQ, this could be an "Untested Issue with latest iTunes and iOS9 having a negative effect on very old versions of iOS being upgraded to iOS9".
I'm writing here to seek help from you, if there is any other solution to this issue, and also to hopefully notify Apple's Support on this issue and hope they will fix it on their next version of iTunes.
Ray Mak (YouTube)