What are the rules according to Zaroff in "The Most Dangerous Game"?
Zaroff's "rules" aren't exactly that -- more like general guidelines than anything else. For instance, he tells Rainsford that he will be released with only a sheath knife, and that he will not be pursued immediately. He also says that if Rainsford survives, he becomes the winner within a single day and night. We may never know if Zaroff intended to hold up his end of the bargain by releasing Rainsford or allowing him safe passage off the island, because in the end, we may infer that Zaroff is killed by Rainsford himself inside the general's own bedroom.
It is interesting to note, however, that Zaroff does display a sense of fair game or sportsmanship at least once during the game. It is near the beginning, where he tracks Rainsford to a tree that he has climbed. The general looks up, undoubtedly sees Rainsford hiding, but then decides to double back down the trail and allow Rainsford a second chance. Such behavior indicates that Zaroff has some sense of fair play, or at the very least, was seeking a greater challenge.