Russia wants to pressure NATO into respecting Russian security interests (red lines), which includes a privileged sphere of influence in their near abroad. Russia wants to dictate which alliances Ukraine may or may not join, and in general what kind of government the Ukraine may have.
As the Russian government sees it, the series of colour revolutions are an example of Western-forced regime change, and Western reactions to the 2011 election protests made them believe that Russia itself is another target. The West, meanwhile, believes that they are supporting Ukrainian (and Russian) civil society in accordance with the Helsinki process when that civil society democratically expresses their will.
Russia sees itself as the successor of the Soviet Union and Czarist Russia. The Czarist Empire never had a breakup like other multi-ethnic empires (Austria-Hungary, the Ottoman Empire) because it became the Soviet Union first and then broke up along Soviet admimistrative boundaries, so there is a mismatch between Russian feelings of how much Empire they are due, and the feelings of the former subject peoples.
During a moment of weakness, Russia and others guaranteed the territorial integrity of Ukraine in exchange for Ukraine giving up to the ex-Soviet nuclear weapons. This was despite the Soviet Union having given Crimea to the Ukraine at a time when both were fellow Socialist Republics in the Union. Russia wanted Crimea back and took it, and it wanted to destabilize the pro-Western government of Ukraine and invaded.
You might read Chapter 7 of this RAND study. An American defense think-tank, but surprisingly understanding of the Russian viewpoint.
So to your question:
- Both sides agree that violating the territorial integrity of a nuclear power would be a rather bad idea. They disagree if the Crimea is Russian territory. They agree that Alaska is American.
- They disagree if Russia still has a privileged sphere of influence like the Soviet Union did during the Cold War. The flashpoints regarding this sphere of influence are mostly in the western part.