All things exists in the past present and future , Is this according to the original teachings of the Buddha?
As I understand, Sarvastivada explains that all things exist in continuity. Nothing comes from nowhere and disappears into nothing, but everything transforms. Therefore the past contains seeds or elements that become things found in the future. In this sense, everything exists at all times, just not in the same form. None of the forms are permanent, but everything that existed in the past, exists in the future, just not in the same way. 

The original teaching of the Buddha said that the notions of existence and nonexistence are two extreme simplifications, and that the truth is in the middle. Things develop into other things, come together, and fall apart.