The difference between Real Air Yezzy 2 NRG, Air Yezzy 2 B-Grade and Fake Air Yezzy 2

Hey Nike Talk, I am a average sneaker collector looking to get a pair of Yeezy 2. I was looking to buy some Yeezy 2 from some guy I know. He told me he had a pair of legit Yeezy 2 but he wasn't going to sell it to me because they were his first pair. He did tell me he had a Pair of B-Grade Yeezy 2 that he would sell me. I was thinking of getting the B-Grades Yeezy 2 just for the time being. B-Grade sneaker aren't that bad I heard, usually it just some minor mistake on the sneaker that caused them to be B-Grade. If I had a pair of B-Grade Yeezy then I could keep me real pair clean. But the thing is I don't know how to tell the difference between a fake pair and a B-grade pair. Can someone please help me out. Thank you and have a nice day.