And one must account for the prophetic relationships of one religion for another. There are obvious problems with doing this - prior religions ultimately reject the interpritations of prophecies later religions apply, and sometimes religionists might be a bit enthusiastic in their interpritations.

Inaddition to the prophetic relationships there are statements in the scriptures, some of which are corrective, of the prior religion.

Is this indicative of diverse religions? Well we do have diverse names and Books to account for. Are they clearly the same religion? From God's pov all things are possible. Perhaps we can find some room inbetween for more than supposing religions happen to have occasional similarities.