What's exactly happening to BTC in Zimbabwe? Why there is nearly 2x exchange rate against world BTC rate? Why can't they use foreing exchanges? Is it possible for BTC to become a national currency? And where it leads?

I'm not sure for bitcoin is the future of banking, but some crypto based on decentralized p2p technology. Due to system is working for herself, every participant work in the system, that work for the benefits of its members.

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For sure! "It is not possible to be ban all around the world", because there is no cenralized server all over the world. All they can do, to block the access to every source associated with BTC: wallets, exchanges etc. While there are prohibitions, there will be ways to bypass them!

In my opinion, when all the bitcoins would be mined, their price will slowly grow up like price of finite minerals (gold, platinum etc.). But there is a problem: if now miners get fixed reward from the System, then this reward would be so little, that mining as it is now, won't be in demand. So, the only way of development when all the Bitcoins would be mined, is "large" transactions with large comission, because there is no other way of motivation for miners