They were not a major portion of Nuclear Weapons R&D and manufacturing were done in Ukraine including design and manufacture of majority of electronics including guidance systems, comms etc. as well as most top tear weapons were designed by Yuzhnoye Design Office (Dnepr Ukraine) and manufactured by Yuzhny Machine-Building Plant (Dnepr Ukraine)
Ukraine indeed had a lot of manufacturing and design of nuclear weapons. Even then the control, launch and timings were all centralized in Moscow. They would have had to reverse engineer and hack a lot of it amidst attacks from Russia and perhaps even the US.
I think you are still confused the control systems were designed and manufactured in Ukraine there was nothing to reverse eng. The only step not done in Ukraine was uranium enrichment.
