How were the Greeks able to conquer or changed the other countries?

Answer 1

There was not an empire in Greece. Greece had two kingdoms, Macedon and Epirus and a number of city-states, some of which were united in leagues, the Aetolian League and the Achaean league.

Mainland Greece was conquered by the Romans in 146 BC. In 148 BC Rome defeated Macedon, the largest and most powerful state, in the Fourth Macedonian War. Two years later it was turned into a Roman province. In the same year the Greek cities of the Achaean league rose against Rome and were defeated. As a result Achaea (in southern Greece) also became a Roman province, so did Epirus (in western Greece). Athens remained formally independent as an ally/client state until 88 BC when it revolted and was subdued. The Aeolian Islands were annexed in 133 BC.