Short answers, pulled from the story.
The Hellenistic period began in 323 BC following the death of Alexander the Great. This event triggered a violent scramble for power among his former generals known as the Diadochi.
Cassander, son of Alexander's leading general Antipater, established the Antigonid dynasty after making himself master of most of Greece. The dynasty emerged to replace the fallen Argead and Antipatrid dynasties of Macedonia.
A coalition of Cassander and other Hellenistic kings defeated Antigonus at the Battle of Ipsus in 301 BC. This victory ended his challenge to the existing order and shifted control over Greece.
Athens lost her independence and her democratic institutions when the cities were eventually defeated during the conflict. Ptolemy II persuaded Greek cities to revolt against Antigonus, but the war resulted in Athenian subjugation.
Macedon was directly annexed by Rome in 148 BC following a rebellion led by an adventurer called Andriscus in 149 BC. This event marked the first of the Greek states to suffer this fate under Roman rule.