Crimea was made part of Ukraine by the USSR and subsequently permanently given to Ukraine by Russia later.
Autonomous region is the term. Not autonomous country. An autonomous region is also the definition of a state within the United States of America.
Nice try though. The rest of your post has been addressed numerous times. Ethnicity of the population has nothing to do with which country has sovereign power over the region. As we've discussed many times already in this thread, under that illogical precedence, Mexico could claim Southern California or Brownsville, Texas. Or the US could claim some of the Japanese islands since US military personnel (ethnic Americans) outnumber the local population.
Do you feel that Russia had or has the right to invade and occupy another sovereign nation that has made no acts of war toward Russia, no acts of violence toward Russia, and with whom Russia has a treaty that precludes such military aggression? Can you please answer the question without the continual "YEAH.. BUT..." responses?