Short answers, pulled from the story.
The Dual Monarchy emerged on the 8th of June 1867 when Emperor Franz Joseph was crowned King of Hungary following negotiations that began on the 20th of March 1867. This formal agreement united two sovereign states under one ruler while maintaining separate governments for Austria and Hungary.
Austria-Hungary formally annexed Bosnia and Herzegovina in October 1908 as a joint holding under Imperial and Royal finance ministry control which provoked immediate diplomatic tensions known as the Bosnian Crisis. Foreign Minister Alois Lexa von Aehrenthal had initially assumed Slavic minorities could never unite against imperial authority yet his policies alienated Bulgarians who turned instead to Russia and Serbia.
The Austro-Hungarian Army conscripted 7.8 million soldiers during World War I while losing approximately four percent of its 1914 labor force in combat deaths alone. The Brusilov Offensive of June 1916 inflicted about one million casualties on Austrian armies that never recovered fully.
German nationalists especially in Sudetenland looked toward Berlin while Czech speakers formed majorities in Bohemia seeking equal status with German language. All public and private schools in Hungary required pupils express themselves fluently in Hungarian after fourth grade by June 1907 leading to further closing of minority schools devoted mostly to Slovak and Rusyn languages.
On the 17th of October 1918 Hungarian Parliament voted to terminate union with Austria marking official dissolution of Dual Monarchy. Emperor Karl issued proclamation recognizing Austrian people right to determine state form while relinquishing participation in affairs on the 11th of November.