What are the causes of an android phone bricking? I will try to change a firmware of SAMSUNG Galaxy J600FN with a current firmware of J600FNXXU6BSK2 with a new firmware J600GDXU3ARH5. I am changing the firmware to bypass the FRP because methods like Talk back, Inserting/Removing Sim card and HushSMS won't work.

Questions:


Will this scenario will be suceeding in changing firmware? 
What are the common causes of the android phone bricking? (Hard/Soft Brick)
If you are flashing ROM, Common causes could be 


Wrong ROM
Battery Failure (Please make sure it is charged fully or upto 70%)
Power Off/ Cancelling process in between.


Please search for the same Model ROM to Upgrade to current version. 
Also in Settings, search for Software Update option before trying anything else.