I would like to know what kind of residential heating was prevalent in Moscow in the time period around 1917 - 1930. What kind of fuel was used? Did they have district heating back then? Otherwise what was used for hot water?
30th years. Most of the buildings are a typical village house. Heating is a Russian furnace. Fuel: woods. Joke: "The city is a big village." In the center of my town there are still many village houses.
More modern buildings along the central streets had heating at the house level. Most often these are administrative buildings. Sometimes it's one boiler. Sometimes a few furnace. Fuel: wood or coal.
Industrial facilities had their central heating boiler. Fuel: coal or foreign spies (This is a joke!).
Mobile version for a one-room apartment - an old furnace-"burzhuyka" ("печка-буржуйка" [furnace-bourgeoisie]). Fuel: wood, coal.
1917-1920 is the time of the Revolution and the Russian Civil War. It was the time of disorder, hunger and, among other things, collapse of public utilities. The population of Moscow almost halved then. As for residential heating, people certainly had to use woods, but if only they could get them.
In 1920s Moscow started to grow at a very fast rate, and the utilities were constantly falling behind in development. So your situation could be very different depending on where exactly you live. Here is the poetical witness from 1935, the excerpt from the poem for children by Sergey Mikhalkov "And how's yours?" (it's about the children chatting about their families and housing issues):
А у нас в квартире газ!
А у вас?
А у нас водопровод!
- А у нас огонь погас -
Грузовик привез дрова -
And we have gas in our flat!
And what's yours?
And we have the water pipes!
And we have the fire went out -
That's a first!
A truck had brought some wood -
That's a second!
So in 1920s in Moscow there were many people who still had no access to public utilities. And it took much time for the government to improve the situation.
The ceramic masonry heaters, in the east are similar to the first one on the wikipedia page (as posted in comments link above) in size, built with ceramic blocks except that they were most commanly square or rectangular, not round. I have seen this type of heating in east german buildings built in the early to mid 1900's as well. I don't have first hand knowledge but I feel sure ukraine, russia and rural areas in eastern europe still use them, because they still do in Romania, even in the central coldest areas. An average house might have two or three of these. It requires quite a lot of work keeping wood cut to fit the heaters in an ongoing manner to maintain a warm temperature inside. Any slow burning organic fuel can be used.