Greg responds...

1. If you mean here at ASK GREG, then no.

2. Anything canon, like the first 65 episodes or the 18 SLG issues, is fixed. Mistakes exist in there, but we try to just incorporate mistakes into the universe. Is Sevarius' name misspelled on his briefcase? Yes. But we assume that mistake happened "In Universe" and that Sevarius got a discount because of the error. Of course, some things that you think you know from watching the episodes may turn out to be not as they seemed. For example, if you thought the Archmage died at the end of "Long Way to Morning" you were wrong. But not because we contradicted what was in the episode, but because when you see "Avalon, Part Two" you are presented with more information that changes what you thought you saw.