Short answers, pulled from the story.
The Kingdom of Greece was officially established in 1832 through the Treaty of Constantinople. This international recognition secured full independence from the Ottoman Empire after nearly four centuries of rule.
Prince Otto von Wittelsbach arrived in Nafplion aboard a British warship to begin his reign in 1832. He was a Roman Catholic ruling over an Orthodox Christian population, creating immediate religious friction with Bavarian Regents initially ruling in his name.
In 1897, the Greek government under Theodoros Diligiannis declared war on the Ottomans after popular pressure mounted over Cretan revolts. The badly trained and equipped Greek army suffered defeat but lost only little territory along the border through Great Powers intervention.
King Constantine I left the country without actually abdicating in June 1917 following the February Revolution in Russia which removed Tsar support for his cousin. His second son Alexander became king while remaining royal family and prominent royalists followed into exile.
The Second Hellenic Republic was proclaimed by Alexandros Papanastasiou on the 25th of March 1924 and ratified via plebiscite month later. This occurred after King George II asked to leave the country following a failed royalist coup and elections called December 1923 formed a National Assembly.
The catastrophe marking the end of the Megali Idea occurred when the Turkish army shattered the Greek front taking Smyrna in August 1922. This led to the evacuation of Anatolia, Eastern Thrace, and islands under the Treaty of Lausanne with over 1.5 million Christians uprooted.