Short answers, pulled from the story.
St. Stephen's Cathedral was founded following the Treaty of Mautern in 1137 and was solemnly dedicated in 1147. The current Romanesque and Gothic structure was largely initiated by Duke Rudolf IV, who laid the cornerstone for the Gothic extension on the 7th of April 1359.
The Pummerin is the bourdon bell of St. Stephen's Cathedral, officially named Marienglocke. It weighs 20,130 kilograms with a diameter of 3.14 metres, making it the largest bell in Austria and the third largest swinging bell in Europe. It was cast in 1951 at St. Florian, Upper Austria, and put into service in 1957.
Yes. On the 12th of April 1945, fires from civilian looting spread to the cathedral, causing the roof to collapse. The cathedral had a limited reopening on the 12th of December 1948 and was fully reopened on the 23rd of April 1952. A Wehrmacht captain named Gerhard Klinkicht also prevented deliberate demolition by refusing orders to shell the building.
Wolfgang Amadeus Mozart was married at St. Stephen's Cathedral in 1782, had two children baptised there, and was appointed adjunct music director there shortly before his death. His funeral was held in the Cathedral's Chapel of the Cross on the 6th of December 1791.
The south tower of St. Stephen's Cathedral stands at 136 metres, making it the cathedral's highest point and a defining feature of the Vienna skyline. Its construction lasted 65 years, from 1368 to 1433.
The Maria Pötsch is a 50 by 70 centimetre Byzantine icon of the Virgin Mary with the child Jesus, commissioned in 1676 from painter Istvan Papp in the Hungarian town of Mária Pócs. Emperor Leopold I ordered it transferred to St. Stephen's Cathedral in 1697 following reports of two miraculous incidents in 1696 in which the painted Virgin allegedly shed real tears.