Generally, no. Most social media apps don't have a built - in feature to inform the person whose story you've screenshot that you've done so. This is to respect the privacy of the user who is taking the screenshot. For example, on Facebook, when you screenshot a story, the person who posted it has no way of knowing. But always be aware that the app's policies could change over time.
No. Since it's your own story, there's no reason for the platform to notify anyone when you screenshot it. It's your content and you have the right to capture it as you like.
Generally, they can't. Social media platforms don't have a built-in feature to notify the person whose close friends story you screenshot. But it's always best to respect others' privacy and only screenshot if it's appropriate and within the platform's terms of use.