No, if you hide your story, people generally can't see it. When you hide a story, it's like making it private and not visible to others on the platform where the story feature exists.
No. When you hide your story from specific individuals, it's intended to prevent them from seeing any related highlights. It's a way to control who gets to view your shared content.
No. If you hide someone from your story, they should not be able to see it. The whole point of hiding someone is to prevent them from viewing that particular story content.
Sure, it's possible. You could, for instance, write it down and keep the paper in a safe place that no one has access to. Or you could keep it all in your mind and never mention it to others.