I'm not a prosecutor, why do I even need to prove something?
You're the one claiming that mere similarity of the serial number to another serial number proves something. It doesn't, as can be seen above.
You have also lied about Tochka-U not being used by Russian forces for "several years", when it clearly was still in use as late as a few months ago, and likely in use during this war as well.
So while Ukrainian government may lack definitive proof, the attempts by Russian propagandists to shift blame are riddled with lies and they're carpet-bombing the internet with contradictory and false information. You're like that boy who cried wolf and blamed the wolf for looting and killing civilians.
Such complex products as a rocket consist of many nodes, assembled at the factory on the same numbers, and each internal node has this number, not painted, but stamped in metal (there are at least a dozen of them inside the preserved tail section). And at the Votkinsk Machine-Building Plant, where this particular rocket was made, the archive has paper accounting documents for each copy, including which military unit it was delivered to.
Nice job shifting those goal posts, comrade.
Let me guess, Russian propaganda will soon produce "factory" paperwork "proving" that the missile in question was delivered to Ukrainian SSR in 1980s.