Regarding the "Su-30MKI tracking J-20 thing" -- from some Indian military followers, the story seems to be unreliable and journalistic aggrandization
More importantly, even if J-20 is claimed to be detected by a radar by XYZ -- remember that the aircraft usually has a Luneberg lens on to exaggrexag it's RCS
More importantly, even if J-20 is claimed to be detected by a radar by XYZ -- remember that the aircraft usually has a Luneberg lens on to exaggrexag it's RCS