What does it mean of my device bootloader Download mode status?

[Coolpixs4]

What does it mean of my device bootloader Download mode status?

This is my device's bootloader download mode ... staus
KG Status: COMPLETED    => ?What does it mean
FRP lock: Off
OEM lock: On (U)    => ?What does it mean

Can I unlock the bootloader and flash custom ROM, is that right?
My device is Snapdragon chip NOT Exynos (I do google search => it is said that snap chipset makes it impossible to unlock boot, is that right?)
Thanks!

[Joeeye]

Honestly, if you're having to ask these questions, I'd suggest not doing what you're trying to do. It's very possible you may brick your device without proper care and so I would advise against it.

[UNKNOWNUSERNAME]

as Joeeye said above, please don't mess with your phones boot loader or anything to do with that as there's a chance you'll brick your phone and it'll be completely useless to you.