Well, it depends on the context of the light novel. It could have cheats related to leveling up quickly in a game - like scenario within the novel. For example, finding a hidden item that multiplies experience points. Or perhaps cheats for getting rare items or unlocking secret areas. Without reading the novel, it's hard to say exactly what the cheats are.
The main distinction of porn with a story genre from regular porn is the presence of a coherent narrative. Regular porn often jumps straight to the sexual action, while the story genre tries to add some kind of story framework around it. But in the end, both are adult-oriented and feature explicit sexual content.
Well, it's hard to say for sure. The concept of 'porn-like' is quite subjective. Some might consider certain novels with excessive sexual descriptions as such, but it depends on individual perspectives and cultural standards.
In many places, 18+ porn comics are considered illegal. This is because they can have a negative impact on society and violate moral and legal standards.
It could be a mortal man. In Greek mythology, gods sometimes had affairs with mortals. Maybe a particularly handsome and charming mortal catches Hera's eye. He might be a great hero or a simple shepherd with a pure heart.