Default Can custom 4.3 or 4.4 ROMs be loaded from TWRP on stock 4.1.2?

I got an i747m for my brother. It was running stock 4.1.2 which I downgraded to 4.1.1, unlocked using the free menu method, and upgraded to a rooted stock 4.1.2.

Is it possible to load TWRP via odin and flash 4.3 or 4.4 ROMs (stock of CM-based) without flashing to stock 4.3 first? If I do flash a custom CM-based 4.3 or 4.4, will this upgrade the phone's bootloader to 4.3 as well?

I'm asking because I want to avoid tripping the knox counter on the phone as it is brand new.

I apologize if these sound like newbie questions. I did a search and could not find an answer.

Thanks for your time.