"Crimeans" are Russians. Crimea was given to Ukraine in 1954 by Khrushchev, before that it was Russia. Of course, this didn't really do anything at the time because both were the Soviet Union. It's only now that it's a problem. Crimea is full of Russian-speaking people and has been for centuries. There are barely any Ukrainian speakers there.

And before it was Russian, Crimea belonged to the Tatars. There are still Tatars left, they make up about a tenth of the population. If you don't recognize the Russians as 'belonging' there, you're left with them. So, restore the Khanate it is, then.

(And before that, there were Goths, but they're all gone, swept away by two waves of conquest and migration.)

Tibet is a different story, as it is full of Tibetans and actual Chinese presence is relatively new (from 1959) and not that big, even if it was a part of the empire before. Chinese people have never really gone to settle there in large numbers, because it is such difficult terrain. It's not very habitable, you can barely even grow crops there. The altitude makes the Chinese sick. The Tibetans have adapted to it over millennia of evolution. China needs control of it because that's where Asia's big rivers originate (and because if it wasn't China, it'd be India). China's been trying to settle Chinese there, but it's not really working, because individual Chinese people usually don't want to go live in a place like that. They'll do it for money but they'll move right back out if they can get similar money elsewhere.