Yes, Snapchat provides a feature called 'Story Views'. When you view someone's Snap story, they can see that you have viewed it. However, there are some ways to view a story anonymously, but these often involve using third - party apps which are against Snapchat's terms of service.
It's possible for them to know in some cases. For example, if they have enabled certain features or if it's a public Snap story and they can see the view count and who's interacted with it. However, for private stories with limited visibility settings, it's less likely they'll know specifically that you viewed it.
Definitely. Snapchat's normal functionality includes showing the people who have viewed a story. Without using hacks (which are against the rules anyway), there's no way to view a story secretly. So if you look at someone's Snap story, they'll know it was you.
Maybe. It depends on if they have any way of tracking or knowing that you rewatched it. Some snaps might have view counts or indicators, but not all do.
In most cases, no. Snapchat is designed to notify you when someone views your story. But there could be rare circumstances where a bug or a hack could enable someone to do it without you being informed.
As of now, Snapchat doesn't have a feature that lets someone know if you've rewatched their story. It's designed this way to give users some privacy when viewing content. For example, if you accidentally skipped a part of a story and want to go back to it, you can do so without the creator being aware that you're rewatching.