Short answers, pulled from the story.
Konstantin Thon is considered the founder of the Russian-Byzantine architectural style. He developed the style in the early 1830s, producing eclectic church designs that combined Byzantine and Old Russian architectural forms and broke from the Empire style monopoly that had previously governed Russian construction.
Neo-Byzantine architecture became an officially endorsed preferred style for church construction during the reign of Alexander II of Russia, which lasted from 1855 to 1881. After Alexander III shifted state preferences toward Russian Revival in 1881, Neo-Byzantine architecture continued to flourish unofficially and remained in use until the outbreak of World War I.
Russian Neo-Byzantine churches are identified by hemispherical domes, the absence of a formal cornice between the dome and its arcade support, wide arched window openings for maximum light, exposed brickwork, and horizontal two-tone striped masonry patterns of alternating dark red and yellow or grey brick. The style used either a single-dome plan derived from the Hagia Sophia or a five-dome plan common in Russian Orthodox practice.
Beginning in 1891, Neo-Byzantine designs spread from the Urals region into Siberia as the Trans-Siberian Railway was constructed. The style followed the railway line, with Byzantine churches appearing in Siberian towns as the rail network expanded eastward. This geographic expansion followed an earlier pattern of Byzantine construction in frontier regions including Congress Poland, Lithuania, the Caucasus, and Central Asia.
After the Russian Revolution, Neo-Byzantine architecture continued in Yugoslavia through the patronage of King Alexander Karadjordjevic, with emigre architect Vasily Androsov alone credited with 50 churches in the interwar period. In Harbin, China, Boris Tustanovsky designed the Cathedral of Annunciation between 1930 and 1941, though it was later destroyed during the Cultural Revolution. Inside the former Russian Empire, destruction of Byzantine churches peaked in 1930, though most buildings survived past the fall of the Soviet Union.
The Poti Cathedral in present-day Georgia, designed by Alexander Zelenko and Robert Marfeld, was the first major Russian Neo-Byzantine church built in reinforced concrete. It was structurally completed in a single construction season from 1906 to 1907, and the entire project from November 1905 to July 1907 set an absolute speed record for the period. The completed cathedral was later demolished.