On CM 12.1 so can i flash stock ROM via odin ?

hi.model is SM-G7102 and is on cm 12.1 http://forum.xda-developers.com/gala...d2-sm-t2949693 but wanna go back to stock so it is possible to flash stock rom via odin ? is this downgrade possible,if yes how ? will nandroid backup help ? :confused: