The danger zone in a novel might vary according to the genre, background, and plot of the novel. In some novels, danger zones could be areas of criminal activity, volcanic craters, black holes, extreme weather, places where terrorist organizations were active, and so on. In other novels, the danger zone might refer to the aftermath of major crises such as wars, natural disasters, and viral pandemics. The danger zone of a novel was usually revealed through the actions of the characters, the changes in the environment, and the development of the plot to make the readers feel danger and fear.
I'm not sure specifically as there could be many different fanfics with that title. Generally, it might involve the unique combat and robotic elements from the Clone Drone in the Danger Zone game, perhaps with new characters or storylines created by the fanfic author.
I can't say for sure without reading the specific fanfic. But it could be the clone drones themselves, or perhaps a new character created by the fanfic author to interact with the existing drone characters in the game's universe.
A 'highway novel' is often a type of story that has a significant part of its plot taking place on highways or roads. It might involve characters on a journey, perhaps running away from something, or going towards a new destination. The highway serves as not just a physical setting but also a metaphor for the characters' paths in life.
The idea of Highway 666 ghost stories is mainly for entertainment. It's a way to add an air of mystery to an otherwise ordinary roadway. There is no scientific evidence to support the existence of ghosts on this highway. People like to tell these stories around campfires or to tourists to give them a thrill, but they are more in the realm of legend than reality.