Short answers, pulled from the story.
The Kingdom of Serbia was founded in 1882 when Milan I, the ruler of the Principality of Serbia, was proclaimed king. The principality itself had existed since the Serbian revolution of 1804-1817 under the Obrenović dynasty.
On the 1st of December 1918, Serbia united with the newly created State of Slovenes, Croats, and Serbs to form the Kingdom of Serbs, Croats and Slovenes, later known as the Kingdom of Yugoslavia. The Karađorđević dynasty continued to rule the new country.
King Alexander I of Serbia and his wife Queen Draga were assassinated inside the Royal Palace in Belgrade on the night of the 28th to the 29th of May 1903. The killings ended the House of Obrenović, which had ruled Serbia since 1817, and brought the Karađorđević dynasty to power.
The First and Second Balkan Wars of 1912-1913 expanded Serbia's territory by 81% and increased its population from 2.9 million to 4.5 million. Serbia gained Kosovo vilayet, Vardar Macedonia, and parts of Sandžak-Raška through these conflicts.
The zadruga was an extended family unit of roughly twenty to forty people who shared land, labor, and property under a single patriarch. Private property did not exist within the zadruga, and land owned by the collective could only be legally divided in exceptional circumstances.
The Black Hand was a secret Serbian officers organization that operated behind the political scenes after the May Coup of 1903. It was also the organization behind the 1914 assassination of Archduke Franz Ferdinand in Sarajevo, providing the conspirators with weapons, maps, training, and logistical support.