Don't worry, in my experience this kind of activation codes stay valid over time.
Regarding the original game, it should be the same be the same i got from the aojiru 5 pack, it's nice that they made it run on modern systems and they added filters so it looks nice even at fullscreen.
btw it seems that you are playing in windowed mode, did you know you can set translation aggregator as "always on top" and put the game in fullscreen =P
They really upped their game with the music, makes you realize how that side has improved since the original, same as the voice acting. I still love the original but some scenes were difficult to enjoy because the music made me sleepy and the voice acting was way too soft.
It seems each character has one loli scene, too bad Momono gets just one but that's better than none at least, the other momos and the trap nekomimi seem to be absent.
lol cute blue slugs, only in Inyouchuu =P
more screens are welcome, helps me wait until monday T_T