thanks a alot, i have successfully update my wm,os and fw.for custom rom:
i believe the fastest rom for 612c is the 6.1 cooked by sergiorus. I haven't really used so I don't know its battery life
for 6.5 rom cooked by me, battery life various among the builds so you have to try it yourself or read other people comment. Performance is ok althugh boot up time won't be as fast as the 6.1, you have try it yourself to see if you like it
did i missing something ?
ill make a review of your cooked rom.