If you are on bootloader version 3 you cannot down grade from Oreo to Nougat.the phone is with firmware 8 security v3
thanks .
Depends on your model variantwhat about root ? is it possible ?
MINE IS:
SM-G950F Oreo
G950FXXU3CRGH
is it possible ?
i trid to install twrp but got :"
custom binary blocked by oem