Avatar the last air bender, series. Questions?

I know a few, when Aan disappeard he was still on that turtle island thing and the ant eater thing couldnt smell him because the turtle blocked his scent, Ozai hates Zuko because Zuko refused to fight him, Katara tried to kill Jet but didn't kill the other man because she was older and smarter by then, I dont know about the letter, I think it was just a gaurd that gave him the letter, and I dont remember Aan killing anyone.