Default [Q] Canvas HD not booting...

I have a rooted stock ROM in my Canvas HD but after installing custom font in the device a pop-up appeared telling me reboot the device after which the device is not booting at all, it is stuck at the boot screen and is not going further. I dont have any backup of the stock ROM nor any functions in recovery mode work like reboot, wipe data/factory reset etc.
SP Flash tool gives error while downloading.

What can I do ?

The phone is under warranty period...