Wasn't sure about your phone model had to Google search it. As far as I know the kg state was only introduced since Pie and as far as I know there is no way to bypass kg state being pre-normal except wait unless you downgrade to oreo. From what I've noticed some models and maybe regions are harder than others.
For my S8 on pie it was easy for me. I flashed pie had rmm and kg state prenormal state with no oem unlock option. Used a variation on date method to get oem unlock. Kg state had changed to normal or is some cases disappeared ( I usually do it a few times from start ) and just left me with rmm state pre-normal. In this state I could flash twrp then root. The only thing I did use was a different no - verity zip as version 6 didn't seem to work for me.
When I did this I only used Wi-Fi connection, no sim card.
One question though you said you still had kg state being pre-normal when you flashed oreo are you sure you are on Oreo if so try flashing oldest version that your bootloader allows.
1. i have OEM unlock shown and it says my device is unlocked
2. my odin mode shows kg state prenormal
3. yes sar i am on oreo
you think i should try some other base rather then latest oreo ? and moreover i cannot even flash twrp so i can move forward
il try without sim card too
thanks again sar