Yes, Mohammed is said to have received the text of the Koran by revelation from Gabriel over a period of time.
The best explanation I’ve read is that the Koran is likened to the Christian belief in Christ as always existing. Think Christ as the Logos. Muhammed may have received revelation but the Koran, as the word of Allah, is believed to be eternal and preexisted it’s revelation to Mad Mo. In that same analogy, Mo is likened to Mary giving birth to the preexistent Christ.
Of course there’s always a minority Shia accounts of Mo reviewing the text of the Koran with Ali. I haven’t bothered to read much about it, only enough to be amused by it.
Given the belief in the preexistent Koran, any versions proven to predate the official historical account will no doubt be explained away.
A linked source would be nice.
Second, if that's the best explanation to be found, it's a pretty idiotic one. Mohammed was a scoundrel of the worst sort before he received his vision and command from Allah to give the Koran to mankind. He is more like a spawn of Satan as is his Koran.
Scriptures in the Bible from the OT existed well before Christ and many, many prophecies came to pass just as prophesied, including the Christ's birth.
Isaiah 46:10 I make known the end from the beginning...
There is no comparison between the two, unless you seriously wish to compare an entire volume of encyclopedias to a first grade reader. And this is just the books included in both the OT and NT. There are many other books not include in our current Bible, such as the book of Enoch, Jasher, ..., there is a long list.
Islam is based on what, three books of questionable origin?
Unfortunately most people don't know the truth. Our churches and institutions have done a horrific job in actually educating the masses, and a major reason we're in the shape we're in.
That's the thing about the Jews, orthodox Christians, and even the Muslims. They do a much better job of getting subject matter into the heads of their people than does Western Christianity. Even if in the case of Islam, the Koran is total BS / or from Satan. That kind of truth telling has contributed to many losing their heads whereas the word of God praise those who question and seek the truth.
There is a lot to learn and no one living today knows it all. But all need to know the basic truth.