He is not in the movie, as most likely his character did not seem to be necessary for the story.

He is not featured in the movie as his subplot was not deemed to be necessary for the film's story. As of now, his fate remains unknown.

He is not in the movie aside from archive footage from the first film, nor is he mentioned. However he can be presumed dead during the Kree civil war. But his precise fate remains unknown.

It is the comic-accurate depiction of the AI. Its design from the first film was criticized by some fans, and this might have prompted the filmmakers to redesign it according to the comics.

Yes, if you want the full context behind them being in the movie. Otherwise, you're just going to get confused.

We know that Carol returned to Earth after the snap. She could have visited a few times to see Maria after everyone was brought back. But once she learned her destruction of the Supreme Intelligence was causing problems for the Kree, she then stayed in space.

The movie hints at what she might have been doing, such as her returning to Hala and destroying the Supreme Intelligence and rescuing other planets, but never fully elaborates on her precise activities.

Likely discarded. As it served its purpose in Avengers.