It's actually not allowing to open superSU, the moment I open, it FCs immediately, there were methods to install via recover but it's not even allowing to flash any custom recovery, it shows success dialogue and download mode shows Peres but on reboot it won't enter recovery
So you flashed the CF-Root through Odin, right?
Get the .apk of the latest version of SuperSU from the internet and install it on your phone. Clear Data and Cache of SuperSU from settings, reboot and try again.
KNOX normally shouldn't interfere this much.
What happened on my first try was that I flashed CF-Root via Odin, the phone rebooted with SuperSU and I opened it and it FC'ed.
A popup window came up saying 'SuperSU has detected KNOX, disable?'
I pressed Cancel.
I went to Play Store, updated SuperSU, restarted the phone.
I still ignored the popup window, I downloaded Titanium Backup and removed all the KNOX related apps.
Restarted again and SuperSU was working fine.