Russia failed in forcing the trading partners to switch to rubel, but the Russian companies are forced to convert earnings into rubel. At the same time most big export companies in Russia are government owned(Gazprom, Rosneft and other resource exporters). So this way the Russian government gets more money, but it increases inflation.

Only if they actually get a peace deal. Otherwise Russia still has EU sanctions and a war going on.

You can exchange it over the counter and it also matters in relation to other currencies.