Ukraine as a state existed muсh earlier than Russia? This is absurd. You are living in some kind of a dream land.
The territory of Ukraine has been the land of Russian people for at  least a few centuries and this has been basically one country populated by the same people during at least a few centuries and this has been going on for more time than the US existed for example.

On the other hand I wouldn't disagree with you on what happened some 10 centuries ago. Why not?

But if you are so willing to go back in time by so many centuries then you would agree with me that roughly 4 centuries ago there was no such country as USA. At that time the territory of the Northern America belonged to Indians and there were no such countries as Canada, USA, Mexico and this list could go on.

Then if we follow your logic then we can come to the conclusion that the US must cease to exist and hand over all power to the Indian population. That would be a fair solution.

So, OK. I agree with your opinon that Ukraine should be a separate country but only in exchange for such countries as Canada, US, Mexico ceasing to exist and handing their territories back to the Indians.

How about that? Why not put forward this kind of a resolution for a vote in the UN? The world needs justice and peace.