Any way to backup FS and main before flashing k750i

[LunatikBunnie]

Is a GDFS tied to a phone or could one model be the same GDFS for all of its own production model?

[flashsim]

Is a GDFS tied to a phone or could one model be the same GDFS for all of its own production model?

As jasmin has noted, GDFS is unique to each phone. That's why it's critical to backup your GDFS before any modification.
It's Step 2 in the XS++ 3.1 Guide