Short answers, pulled from the story.
Soviet commander Fyodor Tolbukhin's troops crossed the former Austrian border at Klostermarienberg in Burgenland on the 29th of March 1945. This military entry marked the beginning of a four-power occupation that would last until 1955.
Austrian politician Karl Renner established contact with the Soviets while living in southern Lower Austria on the 3rd of April 1945. By the 20th of April 1945, the Soviets instructed Renner to form a provisional government without consulting Western allies.
Austrian police records for 1946 showed that men in Soviet uniform accounted for more than 90% of registered crime. This figure stands in stark contrast to just 5 to 7 percent committed by U.S. soldiers during the same period.
Austria received nearly $1 billion through the Marshall Plan plus half a billion in humanitarian aid. This made it the European nation that benefited most from American assistance among all countries receiving such support.
Antoine Pinay, Harold Macmillan, Molotov, John Foster Dulles, and Figl signed the Austrian State Treaty in Vienna on the 15th of May 1955. The last occupation troops left on the 25th of October that year after the treaty came into force on the 27th of July.