Short answers, pulled from the story.
Thespis won the first theatrical contest in Athens around 532 BC earning him the title of inventor of tragedy. He led dithyrambs performed in Attica during rural festivals honoring Dionysus.
Authorities fined Phrynichus a thousand drachmas for bringing personal grief to mind and banned future performances. Herodotus recorded that when this play was performed the entire theatre fell to weeping.
No Greek playwright ever used more than three actors on stage simultaneously. Aristotle claimed Aeschylus added the second actor called deuteragonist while Sophocles introduced the third actor known as tritagonist.
Stone blocks inlaid into hillsides became common practice around 499 BC before wooden seats appeared first. These permanent seats were called ithnoi reserved for priests and respected citizens.
Death scenes always occurred behind the skene considered inappropriate to show killing before audience eyes. This convention persisted until the end of the fifth century BC during Peloponnesian War when the skene reached two stories high.