Justme
I would submit a question.
Always I read to backup gdfs first, and so many time I read -your gdfs is corrupted-.
I have worked with so many mobile and never I did a backup and never I had to use it.

It is very important or not to backup the gdfs?

To Dingle
First of all, to apply a vkp patch you need to flash the main together with the vkp patch, otherwise you got a -false- brick.
Have you tried to flash a main firmware?