I dont mean standard J-10.
Is there any difference b/w J-10B and FC-20
Yes.. the J-10B is a Chinese only aircraft.. the FC-20 will be based on the J-10B.
There were rumors after the may 2 incident that the PAF wanted to rush the introduction of the J-10 by opting for a quick J-10A induction under the guise of a FC-20A.. however these were only from one source and never corroborated.