It would be different this time though. China has shown an interest on the country's crude oil and basically providing the regime a lifeline. Trying to invade Venezuela would be like going to Syria - another world power would push back.
Unlikely, there are no elections scheduled unless Maduro is dethroned. Even if Guaidó takes power, people are talking about at least a year before elections take place.
China would be happy if Venezuela's economy improves, since that would allow them to profit from their investments. Guaidó already stated China has nothing to worry and they truly know business would flourish should the government change. They hoped for Maduro to rectify because he is closer politically, but he didn't; so pragmatically they probably don't mind Guaidó taking power. That is why they remain silent beyond a little diplomatic note and the usual vetoing in the UN council. The Chinese are not stupid, they know the situation. Heck, you can watch the official Chinese news TV channel and get far better information from Venezuela than from watching the official Venezuelan channel which is pure propaganda and zero facts.
Frankly the Chinese would be happier if Chávez was still around, but he appointed an inept to succeed him before his death, and the rest is history.
While the Russians are noisier, they have even less interests in Venezuela to risk messing with (another) conflict. Should America or a coalition act, no one will oppose militarily.