Snape would probably be very conflicted. On one hand, he has a long - standing grudge against James Potter, Harry's father. But on the other hand, he loved Harry's mother, Lily. So, he might be cold at first, but then his sense of protecting Lily's son could kick in. He would likely be very strict with Harry, as he is with all his students, but also secretly keep an eye on him to make sure he's safe.
Snape would likely be initially suspicious. He's not used to Harry coming to him for help or sharing secrets. But once he realizes the seriousness of what Harry is saying, he might start to see Harry in a new light. He could be grudgingly helpful, still maintaining his cold exterior but secretly starting to feel a bit more protective of Harry.
Well, Harry could react with a great deal of suspicion. Since he and Snape have had a rocky relationship, he might think Snape is up to no good. He could try to gather his friends, like Ron and Hermione, to help him figure out what Snape's real motives are. Harry might also try to use his own wits and magic skills to outsmart Snape if he feels that Snape is being unfair or dangerous in his forcing of actions. He could also be very conflicted, on one hand wanting to trust Snape as Dumbledore did, but on the other hand being very wary due to their past interactions.
Well, Dumbledore might be more understanding. He knows Snape has his own motives and might suspect that there's more to the kidnapping than meets the eye. He would try to talk to Snape first. The other teachers would be divided. Some would side with Harry and think Snape has gone too far, while others might wait for more information. The students would be in an uproar, especially those who are friends with the kidnapped person. They'd form groups to try and find out what happened and rescue their friend.
Snape might initially be suspicious. He has always had a distrust of Harry, so he could think it's some sort of trick. But then, as a Potions master and a teacher, he might also feel a sense of responsibility and try to help.
Dumbledore would probably first have a long conversation with Harry. He would want to understand Harry's concerns thoroughly. Then, he would talk to Snape privately. Dumbledore is very protective of Hogwarts and its students. If he found that Snape's actions were truly endangering the students or the school's harmony, he might consider some form of disciplinary action, but firing Snape might not be his first option. He would also weigh Snape's contributions to the Order of the Phoenix and the fight against Voldemort. He has a lot of faith in Snape, but he also respects Harry's instincts and would take his feelings into account.
Harry would probably be very confused at first. He's so used to Snape's animosity towards him that when Snape forgets who he is, it would be a complete shock. He might also be a bit suspicious, thinking it's some sort of trick. But as time goes on, he could start to feel a bit of pity for Snape, especially if Snape seems lost or confused without his memories of Harry.
However, as the story progresses, Harry may start to understand the reasons behind Snape's actions. He could become more resigned and accept the punishment as a part of his growth. He might use the experience to become more cautious in his actions and more respectful of the rules.
Hermione would probably be very shocked at first. She has always seen Snape as a rather cold and unapproachable figure. But after some thought, she might understand Harry's motives if he explained that it was about finding common ground and healing old wounds. Ron, on the other hand, would likely be more openly skeptical and might make some sarcastic comments at first, but eventually come around when he sees the positive impact it has on Harry.