In other words, Russia started from there.
The toponym Ukraine means frontier, borderland of Rus.
Where do you get all this stuff. Do you read it from some forum in the internet or ... ?
You are confusing many things.
The Rus were a people, not confined to the modern nation state of Russia. Modern Russians and modern Ukrainians can both equally claim Rus ancestory. Neither more than the other.
Yes, Ukraine was the center of Rus civilization for several centuries. That it was not the geographical center doesn’t matter. Very few civilizations have had a geographical center.
Indeed, the name Ukraine, as it is now applied, likely came into common usage during the period of Polish control, and its reference to the area as “a border” was in reference to the border of their control. Not as you imply, that somehow it was always considered a border possession of the Russian people.
Ukraine is the real Russia. Muscovites stole their name and now are stealing their land as well.