The MC can take it up the ass in certain situations. I don't remember if it was always clear before you accept sex that she will be the one receiving.
The bonus unlocker is used to see all the bonus images. In the game through out the story there are hidden clickable spots that unlock images. that unlocker does it for you. you'll be able to see them in the bonus section from the main menu. those are not cannon in any way shape or form.