I would expect an invasion to prompt the US navy to put up a blockade, disrupting China's oil supplies and generally making it very hard to keep their economy going. Admittedly, Trump is a wild card; he's random enough that it is hard to be sure what would happen.
Not a chance. Russia has no way to deliver oil in large quantities to China. New pipelines, if they could even build them, would take many, many years.
If renewables was adequate they would not be importing vast amounts of oil.
I do not think China could survive a blockade.