How to go back to stock Android 4.3 from DN3 v5?
Can I just flash it using Odin?
Are you on ND3 bootloader? If you are on ND3 bootloader I suggest you flash back 4.4 stock ROM, but not any Jelly Bean ROM else you will get softbricked because knoxed bootloader does not support downgrading.
It often helps to explain, why you want to do something. You'll get a fuller answer. But I suppose it's up to you. Refer to post 2.