Question: I asked this question earlier: [What "religions" did previous Buddhas practice?](https://buddhism.stackexchange.com/questions/11241/what-religions-did-previous-buddhas-practice/11244)

Now I'm wondering if any teachings from earlier (or later) Buddhas have been passed down to our time. And if not, why?

Answer: 
In Theravada tradition, a Buddha appears in this world only after the teachings of the previous Buddha completely vanishes. It is also mentioned that the teachings of a Buddha will survive after his parinibbāna only if he teaches the Vinaya pitaka.
The Buddhavamsa (a very late addition to the Pali canon) gives accounts of the 24 previous Buddhas. For each of the past 24 Buddhas, it describes the "three occasions of the Buddha's teaching".

They all started by teaching the same sutta (Dhammacakkappavattana Sutta) this is always the first occasion of a Buddha's teaching.

The second and third occasions of a Buddha's teachings vary according to the Buddha involved. For nine of the 24 previous Buddhas, the second occasion was going to Tāvatiṃsa heaven to teach the Abhidhamma.

Some of the previous Buddhas also taught suttas such as the Mangala Sutta.