It's possible. Some people are very observant and might notice if your name shows up multiple times in the viewers list of their story. But it's not a guaranteed way for them to know for sure.
Hard to say. There's no explicit feature telling them you rewatched, but if they're really keeping tabs on who's viewing and how often, they might have an inkling. It all depends on how attentive they are.
Maybe. Instagram doesn't have a direct notification for rewatches, but if they pay close attention to their story views, they might notice patterns or differences that could lead them to suspect a rewatch.