About those preview shots, I'm sure that at least the one with Linda/Caroline/Sara is probably just one of those non-canon screenshots you can find in the game, unfortunately. One of the (few) disappointments that I had when I played it for the first time was that some of the scenes that I'd seen screenshots of, including the title cover (harem!), weren't actually in the game as far as events go.
Still plenty of hot scenes in the "canon", but I still felt a bit let down by the ones I was looking forward to, like Linda going down on Sara, etc. I was wondering and looking forward to seeing what led to that. But the answer was 'nothing', because it never actually happened lol.