Well the reason I ask about the original image of the OS is usually when you root your phone, most instructions state to make a backup (commonly referred to as a Nandroid backup) in TWRP or CWM (recoveries) so that the original image can be flashed if something goes wrong. I can take a look later and try to find an Alcatel forum to try and help, not home atm.
By the way, what site did you get the instructions to root your phone from? They may have instructions on how to unroot as well.