What is a first world economy and why would China be better off with one? China used their export economy to gain the manufacturing knowledge. What would happen

What is a first world economy and why would China be better off with one? China used their export economy to gain the manufacturing knowledge. What would happen if they turn inwards and not allocate their workers on export goods? Which critical infrastructure besides the most modern chips can't they produce? There must be a surplus of workers as long as China has the hukou system. If they can offer free movement to all of their citizens within 1-2 decades, wouldn't that be a good outlook? Russia on the other hand doesn't look good but as the energy and food supplier of China, do they have to maintain their demographics?