Short answers, pulled from the story.
The Kingdom of Greece was established in 1832 by the Treaty of Constantinople, which formally recognised Greece as an independent state following the Greek War of Independence. The country had previously secured autonomy under the London Protocol of 1828 and full independence from the Ottoman Empire by the Protocol of London of 1830.
Otto von Wittelsbach, Prince of Bavaria, was the first king of Greece. He arrived at the provisional capital, Nafplion, in 1833 aboard a British warship. Prince Leopold of Saxe-Coburg and Gotha had been the first candidate for the throne but turned down the offer.
The Megali Idea, meaning Great Idea, was the Kingdom's dominant ideological goal: to annex all lands with predominantly Greek populations and reconstitute a state with Constantinople as its capital. It drove Greek foreign policy from the kingdom's founding through the catastrophic defeat in Asia Minor in 1922, which effectively ended the dream.
The National Schism arose from the dispute between King Constantine I and Prime Minister Eleftherios Venizelos over whether Greece should enter World War I. Constantine, married to Sophia of Prussia and convinced of Central Powers victory, favoured neutrality. Venizelos was an ardent anglophile who sought entry on the Allied side. The rift led to a rival Greek government in Thessaloniki in 1916, French occupation of Piraeus, and Constantine's forced removal in June 1917.
The 4th of August Regime was a dictatorship established on the 4th of August 1936 by Prime Minister Ioannis Metaxas with the support of King George II, who suspended parliament to prevent the Communist Party from gaining power through a hung parliament. Metaxas promoted the concept of a Third Hellenic Civilization, created a national youth organisation, founded the Greek Social Insurance Institute (IKA), and constructed the Metaxas Line of defences. The regime lacked a broad popular base despite these measures.
The monarchy was abolished in 1973 by the Regime of the Colonels, the military junta that had seized power on the 21st of April 1967. A failed counter-coup by King Constantine II on the 13th of December 1967 had already forced him into exile. After the junta's fall, a democratic referendum in 1974 confirmed the abolition of the monarchy and established the Third Hellenic Republic.