1) The "Prophet" contradicts many of the teachings of earlier prophets, eg the teaching of monogamy. A genuine prophet, because he speaks on behalf of God can develop but not contradict an earlier prophet's words. Why? Because God cannot change his mind or He is imperfect and not omniscient (all knowing). We remember, that Muhammad claimed that God changed his mind on which direction to pray to three times (Kabaa, Jerusalem, then the Kabaa again). Strange that.
Monogamy wasn't taught by earlier Prophets. Jacob had Racheal and Leah, Abraham had Sarah and Hagar, both King David and King Solomon has mulitple wives and concubines. Polygamy was practiced by the jews for centuries after Christ, even some Christians practiced polygamy in the early church.
Now, I'm not Muslim. I just wanted to point out the first contradiction you posted was not a contradiction. Sorry. And for Catholicism, there is alot taught by the Catholic Church that is their own creation. Priestly celebacy, etc are evolutions in Christianity, not founded in scriptural evidence.