Yes, NSFW option is only on Itch. The scenes are accessed by playing through the game, they are mostly on Day 2 and two ending scenes are on Day 3. After you get them, you can rewatch them in the gallery.
That I do not know, sorry. The dev will be unavailable until august so I'm trying to answer any questions people have in the meantime, but I never asked about saves in the browser version. If anything, playing the downloadable version is usually always better.
