The Princely State of Sikkim had been invaded by China in numerous occasions. In the past it was an independent country, and was able to hold identity as a sovereign state. Sikkim joined India after independence as it was being difficult for such a small country to keep its people safe from frequent attack by the Chinese and protect its cultural identity.

I'm pretty sure it depends on what their nationality is. If they're Indian, they're Indian. If they're Nepalese, they're Nepalese. I'm an American living in Taiwan. That doesn't make me Taiwanese. My nationality remains American.