“I don’t think they want Kiev. They want most of the eastern Ukraine.”
Then what’s the point of putting some 10,000 20th Guards Army forces in and around Stolin, Belarus? They’re not there to invade eastern Ukraine, they’re obviously there to perform an encircling maneuver around Kyiv.
Army of Observation. It's done to tie down Ukrainian forces away from the battle. I understand the Russians are moving LST's down from the Baltic. So they want Ukraine to defend their Black Sea coastline as well.