Response to both 1 and 2:
because socialism isn't defined by how many people in a country have a certain level of wealth. socialism is the transitional period between capitalism and communism, where the proletariat hold state power and build the conditions necessary for communism. before you can have communism you need to have the productive forces in place to make that economically possible. China chose the route of allowing capitalist investment to help develop its productive forces, while maintaining state power and overall control of the economy in the hands of the Communist Party. they decided that it was better for the country to become wealthy unevenly at first, rather than to keep socialising poverty
What is socialism and what is Marxism? We were not quite clear about this in the past. Marxism attaches utmost importance to developing the productive forces. We have said that socialism is the primary stage of communism and that at the advanced stage the principle of from each according to his ability and to each according to his needs will be applied. This calls for highly developed productive forces and an overwhelming abundance of material wealth. Therefore, the fundamental task for the socialist stage is to develop the productive forces. The superiority of the socialist system is demonstrated, in the final analysis, by faster and greater development of those forces than under the capitalist system. As they develop, the people’s material and cultural life will constantly improve. One of our shortcomings after the founding of the People’s Republic was that we didn’t pay enough attention to developing the productive forces. Socialism means eliminating poverty. Pauperism is not socialism, still less communism
as it happens there did arise a great degree of wealth disparity, which the state has begun to tackle since Xi's leadership took over
and that's something they'll need to iron out over time
but the existence of billionaires isn't a reflection of the class character of the state
you might find this article a worthwhile read https://redsails.org/china-has-billionaires/