Point of reference on dating:
Did you know that the koran was compiled 200 years (at least) after Mo died? From scraps of scrolls, wall scribblings, and tapistries - all of which the original authors were unknown.
There are actually some courageous German academics working right now to compile a critical history of the standard text of the Koran, tracing the very process of redaction you mentioned. Fascinating, isn’t it?