This anime is one of my Top 5 favorite anime :D.
Anyhoo, I have seen all of Code Geass R1, via watching the english dub on Adult Swim in order from episode 1 to episode 25.
As for Code Geass R2, I have only seen episodes 1-10, I am watching the english dub as it airs on Adult Swim Sunday Early Mornings at 1:30 A.M.
Finally, I have only read volume 1 of the manga adaptation of Code Geass R1.