You are asking quite a lot; there is not enough space to write all that you request. So, here are some points to get you started.
One of the main reasons why the Persians were able to rise to power was because they possessed a certain theory of government. They assimilated people and made them a part of their Empire. They even offered quite a bit of freedom. Later the Romans would do the same. Another reason why they were able to rise to power was because of very good leaders. Darius and his oldest son Xeres, were great generals, builders, and organizers. A third reason for the rise of Persia was due to it location. It was able to trade with the other great civilizations in the Ancient Near East.
In terms of the decline of Persia, I would attribute this to the Greeks. When Philip became master of Macedon and took over all of Greece, he made plans to take over Persia in view of the longstanding feud between the Greeks and the Persians. Philip's son Alexander would penetrate deep into Persia and topple the Persian Empire. In the end, all empires are destined to fall. The Greek and Roman in time would follow.