Well, in general, you need to make sure you have the legal right to do so. For example, if it's a video shared under a Creative Commons license that allows for such use, that's okay. However, if it's a private video of someone and they haven't given you the go - ahead, you could get into trouble, like facing legal action for copyright infringement or invasion of privacy.
Well, it's not a good idea. Using someone else's story without their consent is unethical and might get you in legal trouble. You should create your own original content.
Well, it depends. If you have obtained proper permission from the person who owns the story, then you can. But if not, it's a big no - no. Think of it this way, if you wrote a story and someone just took it and put it on their own story without asking you, you wouldn't like it. The same principle applies here. Copyright laws are there to protect the rights of the creators.
It depends. If you have the person's permission, then it might be okay. But if not, it could be a violation of their privacy and rights. There are also potential copyright issues if the story is their original creation.
To get permission, approach the person politely. Explain clearly what your story is about and why you want to include their story. You could say something like 'I'm creating a story about [topic] and I think your story would be a great addition. Would you be okay with me sharing it on my story?' And make sure to respect their decision whether it's yes or no.
It's not enough. While giving credit is a good practice, it doesn't make it okay to use someone else's story without permission. The owner of the story has the right to decide whether they want their story to be on your story or not. Even if you mention their name, you could still be violating their rights, especially if they haven't given you the go - ahead.