The fanfic might also focus on the themes of rebellion and sacrifice. The 'Black Rebellion' aspect can be expanded upon, like how the resistance fighters adapt to new threats. They could be facing a new type of weapon or a more brutal Britannian general. This would show their determination and the lengths they are willing to go to for freedom, similar to what was shown in the original series but with new twists.
The exploration of different relationships. In a fanfic, we might see unexpected romances or friendships develop. It could be between a Britannian and a member of the resistance, which adds a new layer of complexity to the story. This is different from the more straightforward relationships in the original anime.
Yes, it is. As a 'Code Geass' fan, it gives you more content related to the series. You get to explore the story further and might discover new aspects of the characters and the world.
Code Geass did start as a manga. However, its anime version became even more widely known and beloved. The manga provided the foundation for the rich story and characters that were further developed in the anime.
Code Geass started as an anime. The manga was based on the anime's success and came after to expand the story for fans. Some elements might differ between the two, but the anime was the original form.