If Russia did it, and if China finds out, does anybody think China will say, "Well, it's Russia, we'll protest at UN and demand economic sanction"? Moscow and Beijing will be in rubbles when the dusts clear.
Well they were mostly middle-class normal tourists. Probably not important enough for the Chinese leaders to care about.
And I don't think they accidentally shot down the plane. They might've assumed it was a different plane, but from what I could tell, they intended to shoot it down. If I'm trying to avoid accidentally shooting down planes, I'm generally not firing surface-to-air missiles about the place.
It was an arms-length Russian crew then, and that could well have been the case with the other Malaysian plane. Professional support but professional deniability.
reminds me of sting's "russian" song, specifically, "i hope the russians love their children too..."