I managed to downgrade from 4.4.2 to 4.3, what is did is :
Rooted my 4.3
applied chengyu recovery through odin
backed up the rom on an external SD card, removed the card and kept it for reference.
After flashing 4.4.2 and having a camera failed message on every 4.4.2 rom that I tried..
Install the external SD card back, go into recovery, restore... that was it..
So if you have a nandroid back up of your system, you can do it..