Short answers, pulled from the story.
The current International Mozarteum Foundation was founded on the 17th of April 1925. Its origins trace to an earlier organisation established on the 16th of October 1880, which itself grew from the Cathedral Music Society and Mozarteum founded on the 22nd of April 1841.
The International Mozarteum Foundation preserves and promotes the legacy of Wolfgang Amadeus Mozart through three core areas: concerts, Mozart museums, and Mozart research. It organises the annual Mozart Week, maintains Mozart's birthplace and residence as museums, and holds one of the world's largest collections of Mozart manuscripts and letters.
The Foundation is based in Salzburg, Austria. Its headquarters building, designed by Munich architect Richard Berndl, stands at Schwarzstrasse 26, with the adjoining Great Hall at Schwarzstrasse 28. The complex was officially opened on the 14th of September 1914.
The autograph collection contains approximately 190 original letters by Mozart, around 370 letters by his father Leopold, and over 100 autograph manuscripts by Mozart. The Bibliotheca Mozartiana, the Foundation's specialised library, holds around 35,000 titles on Mozart.
Mozart Week is an annual festival of performances of Mozart's works, held around the 27th of January to coincide with his birthday. It was created in 1956 to mark the 200th anniversary of Mozart's birth and draws international orchestras and artists to Salzburg each year.
On the 16th of October 1944, two-thirds of Mozart's residence was destroyed in a bombing raid. The section containing the Dancing Master's Hall survived. The Foundation later acquired the full property, demolished an office building that had been constructed on the site, and reconstructed the Dancing Master's House according to the original plans. The restored museum opened in January 1996.