If, for instance, a Black Mamba bit another Black Mamba, would the venom have any effect on it? Also, if, say, the Black Mamba bit another species, say, a Cobra, would the venom have any effect on the Cobra
Snakes don't usually bite other members of their own species, but yes, when they bite another snake the vemon is effective with varying degrees depending on the species bitten.
Biting should not be confused with eating another snake, where the venom in the eaten snake is destroyed in the digestive juices of the eater. Most snakes that eat other snakes are non-venomous ones.