The Golden Trio's reactions would be diverse. Hermione would immediately start making mental notes about the new magic education system. She would be interested in how they teach Charms, Potions, and Transfiguration in the future. She might even try to get involved in some of the classes as an observer. Harry would be looking for the sense of community and camaraderie that he had at Hogwarts. If he doesn't find it in the future's system, he would be disappointed. Ron would be a bit overwhelmed by all the new gadgets and advanced magic used in the teaching process. He might long for the simpler days at Hogwarts, but at the same time, he would be curious about the new things he sees.
Hermione would start by studying all the new things she could find. Ron would follow Harry's lead most of the time. Harry would use his instincts to figure out who to trust in this new future.
Well, in the future they could encounter different versions of themselves or their descendants. Maybe they would find that Hogwarts has changed a great deal, with new spells being taught that were unimagined in their time. And they might have to face new dark forces that have emerged over the years, using both their old - school magic knowledge and learning new ways to combat the threats.
The founders might be quite surprised by the Golden Trio. They could be impressed with their skills and knowledge. For instance, Hermione's vast magical knowledge would surely catch their attention.
The time travel could put some strain on their relationships at first. Harry might be more focused on seeing his godfather again, Ron could be a bit jealous if Harry's attention shifts too much, and Hermione would be constantly worried about the rules of time travel. But as they work through these issues, they'd likely come out with a deeper understanding and respect for each other. They'd also have to hide their true identities from the people in that time, which would require a lot of trust among them.
They might try to change certain events. For example, they could attempt to save Sirius earlier. Maybe they'd use their knowledge of future events to outwit Voldemort's plans more effectively in that time period.
Harry's personality is deeply influenced by his experiences with Voldemort. In the past, he might be more carefree initially but would quickly become a protector when faced with threats. His presence could inspire those in the past to be braver. Hermione, being the book - smart one, would try to correct historical inaccuracies in magic theory. This could lead to a revolution in the way magic was taught in the past. Ron, with his down - to - earth nature, would probably make friends easily. He could introduce muggle - like concepts to the wizarding world of the past, which might change their view of non - magical people.
The Phantom might also be in awe of the new musical styles and instruments. He could be inspired to incorporate some of these new elements into his own music, creating a unique blend of his classic style and modern sounds.
Harry would rely on his basic values. His loyalty and courage would still be his strong suits. He might join a group of young wizards who are working on some noble cause in the future magic world. Through interacting with them, he'd gradually understand the new rules and customs. For example, if there are new dueling regulations, he'd learn them in the process of joining friendly duels.
They'd probably start off being really cautious around each other. The Golden Trio would be cautious because the Winchesters seem so different and rough. The Winchesters would be cautious as they're not used to this kind of magic. But then Hermione might start asking questions about the Winchesters' hunting methods and Dean would start joking about the Trio's school - like magic.
There's a fanfiction called 'First Year Redo'. In this story, the Golden Trio goes back to their first year and decides to focus on befriending some characters they didn't get to know well before. They also use their knowledge to prevent some small, but annoying things that happened in their first year from occurring again. It's a heartwarming story that shows how much they've grown since their first year at Hogwarts.