Did the Greeks discover particles

Answer 1

Depends on what you mean by "discover". Around 450 BC, Democritus proposed his idea that matter was not infinitely divisible, but made of chunks called "atoms", which each had distinct properties that contributed to the properties of the whole material. This is pretty similar to the true state of affairs, but this was pretty much guesswork on his part. The Greeks never performed any kind of experiments that could confirm the existence of particles.

People didn't really start observing particles like electrons until the latter half of the 19th century, although they had a rough idea that they had to exist prior to that. Protons and neutrons weren't observed directly until the 20th century.