[newbie] galaxy s4 att UCUAMDL topic

hi all , sorry but my english is so bad
i just bought a galaxy s4 att secondhand , this had bassband UCUAMDL . and i checked the lastest version of it is 4.2.2
can i upgrade my phone up to 4.4 ?
and i dont know terminology about "MF3 - MK2 ............."
could you tell me ?
thanks so much :victory::victory::victory: