Short answers, pulled from the story.
The first service of the Datsan Gunzechoinei took place on the 21st of February 1913. Construction continued until it was completed by 1915 despite strong opposition from the Russian Orthodox Church.
Agvan Dorzhiev received permission from the Tsar to construct a large Buryat Buddhist datsan in Saint Petersburg in 1909. He hoped this building would become the residence of the first Buddhist ruler of Russia.
After 1917, the Datsan Gunzechoinei was ransacked and used for many different purposes over time. A Red Army detachment briefly took over and damaged the structure in 1919 before major restoration work began about 1926.
The Buddhist community in Saint Petersburg received official recognition for the Datsan Gunzechoinei in 1989 after decades of silence. That year a service was held by the Most Reverend Lama Kushok Bakula Rinpoche marking the first service in fifty years since the final pre-war ceremony.
The Datsan Gunzechoinei remains the northernmost Buddhist temple in Europe today as of 2013. It serves as a center for the Tibetan Gelugpa school of Buddhism within the city limits of Russia.