No way. Conflicts in two different regions means that its Large Scale War. And in a large scale war Russia use not only nuclear, but also chemical and biological weapons. China (as well as Europe) will lost 90% of its population in less than one year, and survivals won't try to take Ukraine or Syberia.Two possible scenarios of China taking territory in Russia
Russia is too tied up in Ukraine to defend it
Aid in return for aid. If China is good enough in helping us to retake Ukraine and neutralise European threat - Russia will help China to take Taiwan, Japan, Hawaii and/or California.Russia is so dependent on China that it agrees to concessions transferring territory in return for aid