one quick question having a coin graded prevent 100% of fake right?
I've only one coin non graded and I'm a bit suspicious It can be a fake, because it's not and it's in relatively bad shape

I would've thought their job is solely to put a wee score on the lump of metal placed in front of them. I presume grading and authentication are totally different areas and not a problem the average grader is looking to take on. Could be massively wrong though.
I think you are right I do not think they authenticate if the coin or token is genuine or not.
When MJ submitted his he told them it was a fake IIRC.
There are people in this forum who can do a better job at authenticating coins in our hobby than them for sure.
Edit>>> They graded a FAKE Sol Noctis here as genuine
https://bitcointalk.org/index.php?topic=3315347.0;all