[Q] how to go from JB to KK? Very confused. topic

Hi all, Can anyone point me in the right direction? I am on Viper Rom on a SM-N900T 4.3, AND I want to try a KIT KAT rom, but I believe I need to go back to a stock rom first? So I have a few questions...I just got the phone and have been reading alot on it, but to me it gets confusing, and I dont want to brick the phone. I am rooted as well.


Where can I get the stock rom?

I have TWRP version 2.6.3.8 will this work to flash the stock KIT-KAT rom?

I am on BASEBAND N900TUVUBMI7

I read somewhere in XDA that if you go to KITKAT you can't go back to Jellybean?

Just a little confused here, and all the reading just confuses me with all the different models, roms, kernels, etc etc...

Thanks in Advance for the help, Larry