I did't know the Greek-Indian contacts were so extensive for centuries. To add - Persia, also being part of Indo-Iranian civilization, had complicated relations with Ancient Greece, often confrontational but not only. Significant part of Alexander The Great's army settled down in Persia, and not because they really had to. Persia was militarily defeated by Alexander but not quite conquered in a usual sense.
Chinese civilization is a totally different thing.
Chinese civilization is a totally different thing.