The R-26 Rubezh ICBM may have been limited to 4 independent warheads but Russia is on an active war footing for nearly a decade now. I am certain that Russia’s weapons development is moving at breakneck speed. Russia has many fine engineers that can do far more with less money to equal the speed of bloated western defense contractors, SpaceX being the notable exception due to being a visionary.
Break neck speed that cannot even get their Satan ICBM to work after 2 expensive failures.
Yes, and increasing the warhead count with inert or conventional warheads is not too difficult engineering feat.
Could have been done, and the message? You can’t stop these things. Find a way to the negotiation table—sooner is best.