Somewhere i read that Chinese version SU-35 doesn't have L-Band radar mounted on it due to Russian's fear that china may reverse engineer it.
I've read this as well but it started as some forum member simply claiming it with conviction. Doesn't mean it is true. But L-band radars are not difficult technology and China's got experience with them as well. What the Russian's MAY have is software sophisticated enough to make use of those L-bands to identify and target stealth fighters with any meaningful effectiveness. Either way, those claims of Sukhoi fighters being able to see and shoot at US 5th gens (mostly coming from propaganda channels that have a track record of deception and exaggeration) are most likely untrue otherwise RuAF would order thousands of these fighters and upgrade older ones with similar technologies (a TINY price to pay if they can do as claimed) to counter the thousands of F-35s that will proliferate around the world. Likewise, PRC intelligence will have more detailed information on these sorts of technologies and do everything it takes to purchase them, develop them, or reverse engineer them. None of this has been true and while it is possible there are already decent ground based methods of eroding stealth advantages, China is still pouring vast funds into developing stealth fighters, drones, and bomber. Russia is too as far as we can tell for now.