HI GB, thx for sharing your problem with us the muslim community. there is one fact you have to bear in mind that: A prophet, or more accurate to be called Rasul is someone has been chosen by The God to preach to oneness of God. As time progressing, A Rasul only being sent by God to preach to certain region of people, at certain period and place. When a next Rasul came after the previous one, people must follow their own Rasul and obey him. For example, Moses is dedicated to preach the egyptian king and his people, Jesus is for Jews in Israel only. Only then when Muhammad S.A.W came after all of these Rasul/prophets, people must follow and obey Muhammad because he is the last messenger. A last messenger means to conclude all what had brought by all the previous Rasul/prophets. And the preaching of Muhammad is for the whole nation of mankind regardless of race, place, and culture. As a person being born after the Muhammad S.A.W, we are the nation of him and we must follow and obey him. But at the same time, we must also have faith in all the previous Rasul, but not to follow what they preached to their own people at that time. The concept of living that the prophets or Rasul preached is different to each other but the Faith never change, that is Oneness of God. That means syariah and laws maybe different from time to time, as according the suitability of the region and period of time. For example, ancient people had yet prohibited to take alcohol and pork, but if we are follower of Muhammad, we are prohibited to take both. so the jews claim they are follower of Moses and they can either accept Muhammad, but this doesn't mean they obey Muhammad S.A.W. If they obey Muhammad they must accept the oneness of God and Muhammad is the last messenger of God. same goes to Jesus. Even in the original Gospel stated that there will be the next Rasul raised from Arabic land and the mentioned person is Muhammad S.A.W. Original Gospel contains the name of Muhammad but now the bible has been edited. Means the name of Muhammad has been erased and changed to other meaning. This is to avoid Christian to question and then obey Muhammad. So who did the editing, only God knows. Koran did not reveal all to Muhammad S.A.W at one time. Because each verse by verse is revealed to Muhammad according to certain situation and happenings. That is why there is a history behind every verse of Koran. Since each of the verse has its own happening and story, so not all verses are connected or relate to each other, but the truth is there is no contradiction is Koran.