First thing they will teach you in Economics class is the Supply and Demand. And this mainly affects the price of Bitcoin. What is amazing about it is that it is being 'controlled' by the consumers unlike the other currencies which is being controlled by the government. Yes it is volatile and a lot of other factors may affect the price. However, what's good about it is that it is universal and no country has the power to manipulate it's price.
That is so true.
As these countries can limit the use of Bitcoin in their country, they can't stop it completely as no one can actually stop Bitcoin from functioning. Right now with a lot of big names/companies that wanted to invest in Bitcoin, this could be a threat to that decentralization. Nothing may change or everything will completely change in the future.