Believe I read something here yesterday to the extent that China has looked at the Russian performance in Ukraine, plus Russian troop movements out of a number areas toward Ukraine, and perhaps may change their focus on the relatively weakly-defended Russian Far East vice Taiwan.
Don't see Japan doing anything aggressive, unless Russia somehow just collapsed. Believe Georgia is in the same position as Japan.
Merely mobilizing reserves won't be enough. Russia will need to mobilize more trucks from the civilian economy, and believe they will need to draw more food, fuel, and supplies from the civilian economy. With a GDP as small as Russia's question how much can be diverted from the civilian sector to the military without causing hardships in the civilian sector. Could be Russia as a whole has little additional capacity remaining, what with the sanctions. Keep in mind graft and corruption has apparently resulted in insufficient war reserve stocks of food/fuel/ammo/supplies.
This war is now a grind. Ukraine only gets stronger, with the Lend-Lease coming in. The phrase from Winston Churchill, "Give us the tools and we will finish the job" comes to mind. The USA, NATO, maybe Japan and South Korea, and the EU apparently will have relatively few problems keeping Ukraine supplied. Their combined GDPs and transport capabilities very much dwarf Russia's. Question how quickly Russia can replace tank/truck/aircraft/helicopter losses. Doubt China will do much, if anything, to help make good Russian truck losses, which are more important than losing tanks/armored personnel carriers now.
Another piece of WW2 history comes to mind. Italy attacked Greece in 1940, made some inroads. Greeks pushed the Italians out of Greece and into Italian-controlled Albania. Italy started to eventually wear Greece down but in the end needed German help to defeat the Greeks.
en.wikipedia.org
Apples and oranges? Not sure, but certainly worth considering.