After playing all three parts i am here to give a honest rating to this.. I'll give a rating of 7.5/10 i really loved it, the story telling and character development is really nice! However there are few things that personally kind off annoyed me... first, there are no sex sounds as moanings and slapping, the graphics are fine but not great like desirium or realm invader, the first part was 22 days but part 2 was only 6 and part 3 only 5 or so and that kinda made me sad cause i wanted more and lastly, in part 2 there is not the scenes from part 1 and in part 3 there is not the scenes from the rest two... in each part you get its own scenes.. however you keep the photos atleast but mine got deleted in part 3 (i deleted part 1 for extra GB ram so that was probably my bad) anyways, if we ignore the "negative" stuff i give it a 10/10 totally recommend it i cant wait for part 4.
the game is split for android so it doenst get too big for the 2gb limit. leaving the replay scenes from previous parts in would eventually mean there is no room for the story. As to why the first one covers so many more days, it is because as time goes by each day has had more content and renders. To your point about the gallery missing in part 3, yes that was an accident.