Short answers, pulled from the story.
Modu Shanyu united the Xiongnu tribes in 209 BC. This event marked the formation of an empire that stretched across the steppes and forced China to build the Great Wall under Marshal Meng Tian's command.
Temüjin took the title Genghis Khan in 1206. He swept through much of Asia to create the largest contiguous land empire in world history, covering some 24 million square kilometers with a population over 100 million people at its height.
Altan Khan of the Tümed met with the Dalai Lama in 1578 and ordered the introduction of Tibetan Buddhism to Mongolia. Abtai Khan of the Khalkha later founded the Erdene Zuu monastery in 1585 after converting to Buddhism.
By 1911 there were 700 large and small monasteries in Outer Mongolia with 115,000 monks making up 21% of the population. The number of Buddhist monks dropped from 100,000 in 1924 to just 110 by 1990 due to Stalinist purges that killed more than 30,000 people including an estimated 17,000 monks.
Mongolia adopted a new constitution on the 13th of February 1992. This followed a peaceful democratic revolution in early 1990 which led to a multi-party system and the dropping of the term People's Republic from the country's name.
Average annual temperature in Ulaanbaatar makes it world's coldest capital city with January averages dropping as low as -30 degrees Celsius. A vast front of cold heavy shallow air comes from Siberia in winter collecting in river valleys causing very cold temperatures.