No, they are a part of Ukraine. The Russians themselves agreed to that in the past. In 2014 Putin decided he did not like the fact that they were parts of another country so he seized them.
Why is that hard to understand? Haven't you ever looked at a map?
Yes, have you? Russia controls this territory and incorporated it into Russia. That is called reality. Ukraine does not have the ability to take back Crimea. Nor does NATO unless it wants to escalate the war to include nuclear weapons.
The Syrians consider the Golan Heights as part of Syria. The UN has not recognized the lands seized by Israel during its various wars as part of Israel. So what?