Were the dinosaurs before Pangaea

Yes,

When Pangaea broke apart, depending on how it broke apart, was immediately effected by great quakes, volcanoes, etc. But who knows for sure?

The long stood effects were that the continents were broke apart, dividing the populations of dinosaurs apart allowed them to mutate or adapt (depending on different beliefs) separately, thur producing modified species. Also the climates of each broke apart section would have changed from what its original climate was.