The Quran was revealed on Prophet Muhammad via Jibril (Angel Gabriel) over a period of 23 years. It is considered to be the "Word of God". Angel Jibril revealed the knowledge of Quran to Prophet Muhammad without any distortion or omission.
God is in Form & God's Name is Kabir - Surah Al Furqan 25: 52 - 59
Prophet Muhammad's God is referring to some other Supreme God in Quran Sharif - Surah Al Furqan 25:58
Prophet Muhammad's God talks about asking a Baakhabar (well informed) to know about Supreme God - Surah Al Furqan 25:59