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;allIndeed.. I clearly indicated that this was a fake for educational purposes.
Now.... ANACS is simply "grading" these coins. I know you can pay a little extra for them to do research/verify the coin.
Being that, they have since moved away from this with a disclaimer on the back of the slab for any "crypto" themed coins
ICG has seemingly been better. They have been sending back coins that they cannot verify.. ie. I had a coin that the 1st bits were cut off...
They could no verify the coin, so they would not grade it.

This seems to be the correct way to do grading/verification
And yes.. the ever famous graded fake Sol Noctis... loolz.. I might still have that here somewhere? maybe I submitted 2

hahahah
**I would NEVER trust a grading company to authenticate a physical crypto coin. There are plenty of collectors here that are more than well versed in physical cryptocurrencies with years of knowledge and experience**