Yuan is diesel-electric.See Yuan Class sub
Produced, yes, but the airframe and engines are both Russian in design and those are the parts that China has most difficulty with. However, as the J-11 incorporates far greater use of composites and lightweight material than any other Flanker derivative, we can assume that China has been making advancements in the field of material science.You have forgot the J11. Now it's 100% produced in China, sinodefence is just not enough updated on this things.
How many military designs have Boeing came up with since 1979? Lockheed? Northrup?Yet Chengdu managed to come up with two respectable design in these past 30 years