How do Buddhist religion change over time?

Answer 1

That's a good question. From my research there are two answers , the first is Not Too Much and the other is somewhat.

What I mean is this. The core of the Buddha's teachings have remained unchanged for over 2,500 years. All Buddhists agreed to what the Buddha taught and what it means. There is no disagreement to this. So all Buddhists fundamentally believe the same things. This is what I mean by Not Too Much

As to Somewhat, the how of how Buddhism is taught and some supplemental teachings incorporated into one path of Buddhism do exist now and not originally. The Theravada lineage and the Mahayana Lineage of Buddhism are distinct in some ways. Mahayana Buddhism incorporates teachings and wisdoms from later Buddhas and Bodhisattvas that Theravadeans do not fully recognize. But these newer teachings do not fundamentally change Buddhism, they explain or provide illumination to the Buddhas teachings. The teaching methods used are different between the two lineages also. But this, as I have said, is mostly window dressing compared to the fact that the core is always the same.