Re: What will happen to the Bitcoin network if Russia blocks access to the internet?
Well; Let's say that in the first instance those who live on the border, where literally the cities are separated by a few meters, there is cellular connections available, of both countries, in this case one of them would be blocked.I have been in border places where the Internet connection is better in Mbps that the neighboring and literal country sell these connections with the use of antennas that you can get on ebay and then an antenna point to point of the other side of the border works.
Then you've never been to a Russian border. 
This shutdown will probably most likely include Belarus, this is how Belarus borders to western countries looks like:
with the Baltic states, the border is mainly a lake and a river and there are almost no Russian villages there the rest will be with Ukraine, lol, and Kazakhstan, Mongolia, and China mainly, champions of freedom and countries known to let poeple host free internet connections.
All the borders have been exactly cut like this strategically, remember it's the Russia we're talking about, this is not a border between Belgium and Netherlands.
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The point is that, as I said, the block would never be 100% effective, although it may seem so in this case, there will always be something that can be done or tried. I suppose that this blocking would come with a law similar to that of false disclosure (news) that brings prison sentences, so will be added to avoid these initiatives.
In any case, without a doubt, there is no comparison, geopolitically speaking, but in my region there are such complex borders in the types of