Well, how long have you been in fandom? Plus, these aren't all going to apply to everyone. And a lot of these things are things that took place in 1999-2001.

And a lot of these are things I know more about than I experienced myself. I read the first edition of GoF, and yet, didn't even notice the Wand Order mistake. And I knew about Harry's schoolbooks, but didn't actually buy them until I realized everyone and their brother used them for fanfic reference.