samsung tab3 smt310 how mod official firmware for knox 0x1

hi here my first post

i wonder some help for get some tools who make me able to mod an official firmware for
samsung galaxy tab 3 8.0 smt310
just for change the knox to installation by odin mode
i hav rooted it then i encouter some difficulty and system folder were corrupt so after a while i upload inside my tab an custom firmware but that doesnt make me happy at all at first i was trying to get back to original first firmware rom as i bought it.

so after looking everywhere i understand that once you erase the nand, the knox protection not allowed you to install official firmware
that's why i asking you some help after pickin up an official firmware jb4.2 date of 03.06.2013
i see tar file can be unzipped found 6 files img and two bin files.

my question is simply if mod a firmware to make it custom is madded by most of poeple i just trying to mod my by simply changing the firmware as custom for it past as knox 0x1

anyone have some tool or tutorial who can help me?
my goal is just to get back to origin firmware even with knox 0x1
a custom firmware but not custom just changing for be able to reinstall it

thank you

samsung galaxy tab 3 8.0 smt310
with even not a trwp or cwp knoweldge

thanks

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