Egypt are the Ptolemaioi.

Alexander the Great conquered Egypt and it was a part of his empire. When he died his empire was torn up between squabbling generals. Ptolemy took Egypt, therefore it is called Ptolemaioi.

Egypt became culturally similar to Greece due to the fact that it was now owned by Greeks and was no longer ruled by pharaohs.

The same is true for Arche Seleukia and Baktria. Arche Seleukia is a chunk of land that was conquered by Alexander the Great. When he died, that chunk of land fell into the hands of one of Alexander's generals and became its own nation, seperate to the other chunk of his empire, Egypt, which was claimed by another of his generals.

Baktria has Greek culture because it was also conquered by Alexander the Great, but in 250BC i believe, Baktria rebelled from Seleukid rule and declared its independence.

Like i said in another thread... Read read read! Read everything. Alexander the Great took Greek culture to the ends of the earth. That's why most of the eastern half of the map has Greek culture and Greek generals... They're Greeks that settled there when Alexander the Great (a Greek himself) conquered them!