You just post a picture of a serial number painted on a missile, there is no context, no visual reference, it could be one of my cars painted in green with a few numbers and on top you assert that it was part of Ukraine's arsenal.
The serial number ending in 79 seems to be real - it can be found in TG La7 (Italian TV channel) video on Youtube.
But you're right about the rest of that "proof" is coming from Putin's mouthpiece (RIA) so it can't be trusted.
It was quite lovely though how our favorite Kremlintroll announced that a serial number would be the ultimate "proof" and sure enough, "proof" soon appeared.
There are easier ways to determine the culprit of what happened - for example, check the serial numbers on the tail of the rocket
there is information about the serial number of the rocket from Kramatorsk
Agreed, I am just saying that, in that picture, there is no context to link it to anything in particular, nor can be really validated as original.
Now that I think of it, could a serial number be just faked? I mean, is not like you are changing the directional system.