Originally Posted by gaww
I have read that after even just flashing 4.4.2 update, it will not be possible to revert (nandroid) to any 4.3 ROMs. If true - why if firmware the same ?
This is what I've read: if you update to official 4.4.2, you cannot flash back to official 4.3 in Odin
. Likewise, if you updated to official 4.3, you cannot Odin back to official 4.2.2. If you try to, you'll soft brick. The Knox-secured bootloaders prevent Odin from successfully flashing a previous version.
Now, if you do this and therefore soft-brick, you need to pull the battery and re-enter Odin mode. Then you must Odin-flash a custom recovery (luckily there are some Odin-flashable recovery files out there). Then, after another battery pull, you need to manually boot into your custom recovery and flash a custom rom (or restore a Nandroid). This will save your soft brick.
What we don't know, because it hasn't been released yet, is if the official 4.4.2 tar file would successfully flash in Odin if you already have the 4.4.2 Knox bootloader.