Buddhism have likewise seen changes throughout their histories
Not really. Buddhism has evolved into different traditions, but Vajrayana has remained as it was founded ( just a few generations after the Buddha's death ) for its entire history. Buddhism has a large variance in tradition but just like other Christian denominations - its no different. Doctrine-wise, Buddhism has remained largely the same with Theravada, Mahayana and Vajrayana all keeping lockstep with their doctrine for the most part.
Instead of saying something you're not sure about just say "I don't know."