War in Europe-Can Putin Invade all of Europe?

Russia has the only army in place  in Europe of their size and stands ready to assume the army of Ukraine.  China is unlikely to enter into any conflict since it is currently engaged in a war to the death with the United States and USA involvement in Europe would only play into their hand better as would the weakening of Russia.  In point of fact, directly or indirectly, China would supply technology and equipment to both combatants and Russia would have a shorter supply chain.
Europe would not have adequate fuel supplies in the event of an evasion and Russia would.
Russia has no exposure to the north and for all intents and purposes their western borders are secure.
More importantly, they have developed a model for destabilization and invasion.  Yes, they borrowed it from Hitler, but that's not really news nor is it a problem.  These things that work tend to repeat themselves.
In times of war, intelligence shuts down and group intelligence (which isn't) takes over.  Hence, depending on what allies Russia can take on, they can count on support from their population.  In addition they have a sufficient army and plenty of aging veterans to draw down on in the event their were large casualties, which is not likely.
We are not discussing holding land, we are merely talking about invasion.
There are good roads that can support Russia's tanks.  There are good airports that can support Russian aircraft.   There is not an effective plan in place to degrade these.
Russia would have to consolidate and build up their arm under the eyes of Europe without having time for a scortched earth plan to be put in place, but they have the opportunity to do this by pretense, that is building a largely unnecessary force near Ukraine and west on the borders of Minsk and the other break away republics.
Nuclear weapons are difficult to limit and this means they favor those willing to accept limited losses.  It is unlikely that anyone would protect Europe by destroying Russia since the net effect might be Armageddon which some would pursue as a knee jerk reaction, but a Russian Europe is not half as frightening as what will happen once China has successfully defeated the United States which is equally eminent and if you don't think the war with China is real, I suggest you read China's weaponized economy.  It explains why you're sleeping through the largest and most successful military campaign of all time.
I suppose, simply put the answer is yes.