Now it is true that prophets were sent to all peoples and to all nations, and that these religious codes have differences according to the requirements of the time and of each specific nation. However, for those who have studied the major religions of the world, you find a striking commonality in the teachings of all religions. In essence, all religions actually carry the same teachings at their core.
And there is one simple reason for that: they are all from the same one God.
In reality, the prophets are actually like a relay team in time, each passing the core teaching forward and successively adding to it, in a process of religious evolution through which God taught more and more refined levels of morality, spirituality and more robust teachings to cover the increasing complexities of life, all in accordance with the gradual spiritual development of humanity.