Russia's opinion on others' borders is relevant only to Russia.
I think Moscow is part of my estate and that I'm entitled to take as much money as I can from any Russian national I encounter as compensation for Russia's illegal occupation of my house. I don't think that's a crime, so it's not a crime. Is that how this works?
No, under your hypothetical it's still a crime, but it's not admitting to a crime. You haven't pled guilty, you are still asserting a defence to the accusation (that you own Moscow).
If you had a sufficiently powerful military to back up your opinion on the ownership of Moscow, then that would indeed be how it works. International law does not have courts with the same amount of power as "normal" law. If countries are at odds the options are basically a sternly worded letter, economic sanctions or military action. And, of course, the target of such action can strike back in much the same ways.
Understandably, not many countries are willing to enter hostilities with Russia.
Russia does not really need to sanction anyone at the moment, they already have Crimea under their control and no country with a strong enough military cares enough to take it away from them and give it back to the Ukraine.
Depends on the meaning of the word 'within', I guess...