Not sure you can, at least not in W10. I think security is at the user level so if you don't want someone to see a folder you need to give them their own Windows account. OTOH I think you can share folders between accounts,
Bitcoin isn't money though is it? i.e. a medium of exchange. Who is using it to trade commodities and which commodities? How much Bitcoin was used in such transactions?
Bitcoin has not replaced any established fiat currency. Like all the other cryptos it is used as a traded security and valued...
It's just an attempt by Sunak to create yet another wedge issue between the tories and labour. When this one fails he will then pivot to attacking disabled children and puppies.