Default [Q]help updating sph-L720

Hello,
after a few days researching and trying to root/flash my samsung sph l720 i didnt found anything but first:

a cousin brought me his gs4 l720 from us, it was unlocked and i can "use" it but i cant enable the hotspot etc...
i was almost going to root it but i started reading about knox, bootloaders etc thats why i wanna ask if its possible to update it from 4.3 to 4.4 and enable the hotspot etc.

software version:
L720VPUAMDC

Hardware version
L720.08

Android Version:
4.3

baseband version:
L720VPUAMDC

kernel version:
3.4.0-1927016
se.infra@R0301-10 #1
Sat Nov 16 11:05:09 KST 2013

Compilation number:
JSS15J.L720VPUEMK2

thats all the info in about device... i wanna know if its possible to root it and install a custom recovery like CWM
also if its possible to update it to KitKat

what happend if the Knox flag triggers ? do my s4 bricks or something ? or it just voids the warranty, because i dont care about the warranty as im in another country.