Muhammad's first revelation is that he must only worship one god and one god only. It is D. He must worship and obey only Allah (God).
It may get weaker or stronger depending on laws , legislation, war ,and economics.
The Quraan was verbally sent down in parts to The Blessed Prophet Muhammad (peace be upon him) by the archangel Gabriel (Jibril) at the age of 40. The Quraan was finally compiled after the Prophets' death at 63 during the ruling of Umar son of Khattab (RA).
Please do NOT quote me on this. I will look further into it if needed.