`Not very stable
Iran had a monarchy before 1900. Qajar monarchy.
Mohammad Reza Shah Pahlavi was the Shah of Iran from 1941-79. He was deposed by the Islamic Revolution in 1979. After the Islamic Revolution, Iran changed its form of government to an Islamic Republic, and control was given to the leader of the Revolution: Ayatollah Khomeini. This new form of government is the form of government in present-day Iran, as well.
a democracy .
A government that rules a country form year to year without great change is usually a republic government. The power is usually with the people but only some of the people rule.
Neither is actually a viable, stable form of government.
Democracy
Iran uses Tyranny in modern times. In 1939, Iran used it.
the enlightenment philosophers affected our current government by giving us more individualism, and the basic belief in equal rights.
Democracy is not necessarily the BEST form of government, however human experience over many thousands of years has proved that a democratic system is : Stable, Effective and Fair. Please do NOT confuse democracy and capitalism.
Federal Democratic Republic of Nepal President as head of the state and Prime Minister as head of the government.
because Europeans changed the whole government style of ruling
The CIA World Factbook calls Mali a semi presidential republic.