Short answers, pulled from the story.
Russian icon painting began after Kievan Rus adopted Eastern Orthodox Christianity from the Byzantine Empire in AD 988. The earliest icons followed Byzantine artistic standards directly imported from the Eastern Roman Empire.
Andrei Rublev, who lived from around 1360 into the early 15th century, is considered the preeminent Russian icon painter. His most famous work is The Old Testament Trinity. The Moscow Patriarchate officially recognized him as a saint in 1988.
In the mid-17th century, Patriarch Nikon instituted changes in liturgy and practice that split the Russian Orthodox Church. The State Church began incorporating Western European realism into icons, while the persecuted Old Believers maintained the traditional non-realistic Byzantine style.
In Russian, as in Greek, the same verb pisat means both to paint and to write. Icons are considered the Gospel in paint, so the act of creating one is described as writing rather than painting.
Soviet government agents destroyed many Russian icons and sold others abroad. Some were hidden by their owners or smuggled out of the country. Icon painters in Palekh, Mstyora, and Kholuy redirected their skills to lacquerware, giving rise by the mid-1920s to Russian lacquer art on papier-mache.
Russian law prohibits the export of any icon more than one hundred years old without a certificate from the Ministry of Culture of the Russian Federation. Despite this restriction, icons over that age are regularly smuggled into neighboring Baltic countries or exported with fraudulent ministry certificates.