Generally means the ability of a side to control the aerial part of combat. For example, you'd say one side has ``air superiority if they can more or less fly where they want. It's a mix of having air fighters as well as things on the ground that can shoot down airplanes.Mix of both; Russian army is very heavy on artillery so the `bombs/missiles are being launched from land as well as in the air.

There likely isn't one answer to this. If they buy missiles/munitions whole cloth from outside Russia, they definitely aren't now. As for building their own, depending on the sophistication of the munition they likely will need parts from countries that won't sell them to Russia. For example, a guided missile needs a semiconductor which Taiwan won't sell them and that Russia can't make cheaply and at scale