AFAIK you didn't get the picture that is the last but one (the one) on the bottom left in the menu?
That should unlock automatically if you reach and watch the bad ending (Don't hit Alt+F4 before the unlock-sound rings).
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Thanks let me hope that your point and click adventures will be female and also have them remain naked without any clothing
and still one doubt how will I unlock every nurse in the game and then undress them naked,how will I see a naked nurse in the credits and also give me a cheat to let me win this difficult secret level this instant.