One effective moveset for Cofagrigus could be Shadow Ball, Will-O-Wisp, Protect, and Toxic. These moves give it a mix of offensive and defensive capabilities.
Itachi's personality could become more outwardly friendly. In the ninja world, he had to keep many secrets and be aloof. But in the wizarding world as Harry Potter, he might find it easier to let people in. He may also be more assertive in a different way. Instead of silently following orders like in his past life, he could take the lead in situations, using his own judgment based on his past experiences and newfound magical knowledge.
A possible relationship could be one of mutual respect. Sarada would respect Itachi for his skills and his past sacrifices. Itachi, on the other hand, might see Sarada as a symbol of hope for the future of the Uchiha clan. They could share stories about the Uchiha, with Itachi passing on the history and traditions that Sarada might not be fully aware of. This could strengthen their bond and lead to a deeper understanding between them. In the fanfiction, they might also team up to face a common enemy, relying on each other's strengths and abilities, which would further solidify their relationship.
Kid Itachi was a prodigy in the Uchiha clan. He was extremely intelligent and showed great talent in ninjutsu from a very young age. He was quiet and often seemed to be deep in thought, different from the other boisterous kids. He was also very kind - hearted, which was a bit unusual considering the somewhat cut - throat nature of the Uchiha clan at times.
Sure. Itachi's saving of Sasuke was a crucial moment in the manga. It was tied to his hidden motives and sacrifices for the greater good of the ninja world and Sasuke's future.