example: "CAR’s analysis, based on physical examinations of marks on the remnants, shows that the missile that struck Okhmatdyt hospital was produced at most three months before the attack. Or perhaps even eight days before. " [1]
Sanctions and limited parts availability are limiting Russia's ability to manufacture weapons [2]
[1] https://global.espreso.tv/russia-ukraine-war-car-researchers...
[2] https://www.kcl.ac.uk/warstudies/assets/kcl-fasi-paper31-win...
Ukraine, well they don't have nukes but as I understand it, much of the USSR's nuclear arsenal was built in Ukraine. I suspect Ukraine could respond tit for tat.
Buildings in Kiev aren't made out of wood. Firebombs would do very little damage.