Russia never sells China it's most advanced weapons systems. That's reserved for India. Also Russia doesn't have to worry at the moment cause they are 10-20 years ahead in military R&D. It will take a while for China to catch up but they are doing so at a rapid pace. Still Russia will milk China for what they can as they know they can't forever. China will one day catch up and perhaps overtake them in military technology with or without Russian assistance. They can afford to spend vast sums on R&D.
About the aircraft carrier, I hope China doesn't go the way the US has with a gigantic offensive military, 800+ military bases worldwide and 10+ aircraft carriers. However as long as the US continues to have a huge military with an offensive posture and dominate the Pacific the way they do then it seems like China will invest huge sums in upgrading their navy and other military branches to deter the US. They full well remember when Clinton sent in a couple of aircraft carriers to deter them from influencing the Taiwanese elections with hostile acts. Of course nowadays the US wouldn't be able to get so close to China like back then as China has much better equipment now.
