In this kind of fanfiction, Jotaro might change some crucial events. For example, he could prevent some of his friends from getting hurt or even stop the main villain from starting their evil plans at an earlier stage. This would completely change the original story's timeline and create a whole new set of adventures and challenges for Jotaro and the other characters.
Perhaps Jotaro would use his knowledge of the future to gain an advantage. He might seek out allies he didn't have before or train in different ways. He could also try to figure out the secrets of the Stand powers earlier, which would give him a stronger position against his enemies. And it's possible that his relationships with other characters would develop differently, like with his family or fellow Stand users.
He could meet his past allies in a different context. For instance, he might encounter Kakyoin or Polnareff when they were just starting their journey. Maybe he could also run into Dio at a time when Dio was still plotting his rise to power, which would create a very tense situation.
He could change the course of major events. For example, he might prevent the rise of a powerful villain. This would have a huge impact on the entire galaxy. Maybe he could save some characters who died in the original timeline.
In this fanfiction, Sora might change key events. Maybe he could prevent some of the tragedies that occurred in the original story. For example, he could save a character who was lost before.
She might change important events in the wizarding world. For example, she could prevent certain dark magic incidents or save characters who died in the original timeline.
Well, he might meet his ancestors. It could be really interesting to see how they interact and what kind of influence he has on their lives. Maybe he'll change some small events that end up having a big impact on his present time.
Well, he might prevent some of the villains from ever becoming powerful. For example, he could stop Frieza from getting all those power - ups.
Well, she might meet historical figures. For example, she could encounter Cleopatra and have an interesting conversation about ancient Egyptian politics and culture.
In the 'Petunia Goes Back in Time' fanfiction, she might try to change things that happened in the past. Maybe she wants to fix a mistake or prevent a bad event from occurring.
One possibility is that Draco could try to change his family's fate. In the original story, his family was on the wrong side of the wizarding war. By going back in time, he might attempt to steer them towards a more positive path, perhaps by preventing them from getting involved with Voldemort in the first place.
He might change the course of some major battles. For example, he could prevent the destruction of certain planets that were destroyed in the original timeline.