The value of a share typically comes from the productive assets the company owns. If you buy all 468 million shares of QSR, you get all the restaurants, the brands, the vendor relationships, the employee relationships, the customer relationships. If you have a smaller fraction, you have a smaller fraction of that, plus you are entitled to a share of the profits generated.

But if you buy a Bitcoin, you own no productive asset and therefore are entitled to no profits. At one point the theory was you could trade it for something useful, like other currencies. But it's a pretty bad currency, so people mostly have stopped pretending it is useful for that.

There are answers to the rest of your questions, which are complicated and depend on exchange and jurisdiction, but people can look up the details if they want.