Firmware variant plz help

Hi
I had read many articles about how to flash stock Rom, It’s confusing
How we choose the appropriate firmware :
1/MID and CID
2/MID, CID and main version (the same or higher)
3/MID, CID, main version (the same or higher) and the same basbande(Radio)

Plz help this is will help alot of beginners.

Thank you