I don't remember if "pre iOS" Safari had a version listed anywhere. You would likely need to look in system code to find that out. I have no idea how to do that myself.
I am curious, however. If the iOS has no (official) listed version - why would you expect an app that is integrated into the system to have its own version number?
And, if it DID have a version number, how would you determine which iOS that used?
Of course, iOS, as a system identifier, did not yet exist.
You are on some kind of wild goose chase, eh?