No, you can't bing up any details you want. The subject of discussion is the first Godfather movie. If it's such a good movie, it should be able to stand on its own. What happens in the other movies or in the book does not matter. What matters is what happens in the first movie. Imagine this was 1972, the firs movie just got released. We both have just been tortured by being forced to watch it. Would you be bringing elements from the second movie to explain the crap job they did in the first, even though the second movie hasn't been made yet? No, you wouldn't because you couldn't. So again, try to keep the discussion focused on the first movie.