4. Fredo's character is completely changed from the novel to the first movie, and changed quite a bit again from the first to second movie. Fredo was learning under Moe Green. By GF2, Moe is gone and the Corleones have four hotels, so you'd think Fredo would be of some use to the family. Instead, he's running brothels and seems to be someone Michael wouldn't take a meeting with if Fredo wasn't his brother. What happened? We don't know.

6. What everyone knows about the Senate hearing is one of the most curious questions in GF2. We know the Senate lawyer Questadt was right behind Roth in Havana, in Michael's direct line of sight. Why? We don't know.

8. I'll suggest again that Fredo may have some motivation based in sexual frustration. This is evidenced by the deleted scene (which I think is included in some versions) where he and Deanna arrive at the party, by Deanna's mocking of him at the party, and by his confession to Michael that Fredo should have married a woman like Kay. It's all reminiscent of the very opening of the novel, where Johnny [edit] has professional problems but hits rock bottom because he can neither subdue nor satisfy his movie star wife.