My educated guess is that there is NO way torah and its study was similar in the times of the early prophets to the way we know it today.
The Am ha’aretz of back then would probably be what people consider a rabbi today.
The reason for mahlokot later on probably came as a result of 2 exiles, which prove to be very taxing on the jewish people and our culture.
I would assume that the Torah that was learned back then was amazingly expansive, and the only questions were philosophic and interpretational, not halachic- how could you have the questions like washing on pizza when you lived in a generation so close to moshe and matan Torah?