the backup can be made with MTKDroidTools only if the phone is rooted ( In root/backup/recovery tab ). There the application reproduce the files for FlashTool and saves them in backup folder, is pretty simple. The rooting proces is extremley simple with the tool mt6589_rooter (
http://www1.zippyshare.com/v/29239903/file.html uploaded right now, 2 Mb size), just enable usb debugging and access run.bat
And in setting > About, the phone model is S138 not XY100 or anything else, damn chinese phones...