Even in some more edgy or modern literature, the focus is still on complex human emotions and social phenomena, not this kind of private and inappropriate behavior.
First of all, it's an embarrassing situation. You should try to stay calm. Maybe start by apologizing for the inappropriate behavior in a private moment. Then, it might be a good idea to have an open and honest conversation about privacy and appropriate boundaries in the future.
This is a very uncomfortable situation indeed. You should start by taking responsibility for your actions. Let your little sister know that what she saw was not appropriate for her to see. If she has questions, answer them as simply and appropriately as possible. For example, you could say it's a normal but private activity for adults. After that, work on your self - control and privacy habits to avoid similar incidents in the future. It's important to also respect the fact that this might have an impact on your sister's view of you, so be extra careful in your interactions with her going forward.
Getting caught doing such an inappropriate act in school would likely lead to severe disciplinary actions. You could be suspended from school, face expulsion in more serious cases. It also would seriously damage your reputation among peers and teachers.
Yes. Consider a story where two teen boys are part of a school's science project team. They work hard to build a model of a solar system. They stay after school in the science lab, discussing how to make the planets look more realistic, measuring the distances accurately, and painting the models. They support each other when they face difficulties, like when they can't get the orbits right. It's a story of their cooperation and friendship.
It's most likely a rumor. There are a lot of unsubstantiated stories floating around on the internet. Without proper evidence, it's hard to believe such a disturbing story could be true.
The teen should probably first stay calm and avoid overreacting. It's an extremely awkward situation, but panicking will only make it worse. Maybe quickly cover up and apologize for the inappropriate behavior in a place that should be private.