For starters, the risk-free rate has nothing to do with stocks. It would be independent of anything. It pays out the same return in all states of nature. The definition of a risk-free asset is that regardless of how the universe turns out, including a meteor striking the Earth killing everyone but the recipient, then the payout would happen exactly as planned. One could imagine a computer still being on, connected to a power supply and printing a check. Most people use the 90-day t-bill as the risk-free rate. A beta greater than one implies it is more volatile than the market, not that it moves more perfectly.
The CAPM should not be used for this. Cryptocurrencies should not be used with this model because they have valuation dynamics related to the new issue of coins. In other words, they have non-market price movements as well as market price movements.
In general, you should not use the CAPM because it doesn't work empirically. It is famous, but it is also wrong. A scientific hypothesis that is not supported by the data is a bad idea. My strong recommendation is that you read "The Intelligent Investor," by Benjamin Graham. It was last published in 1972, and it is still being printed. I believe Warren Buffett wrote the current forward for it. Always go where the data supports you and never anywhere else, no matter how elegant.
Finally, unless you are doing this like a trip to Vegas, for fun and willing to take the losses, I would avoid cryptocurrencies because you don't know what you are doing yet. It is obvious from the posting. I have multiple decades working in every type of financial institution and at every level, bottom to top. I also have a doctorate, and I am an incredible researcher. I am professionally qualified in three different disciplines.
If you want to learn how to do this, start with the "Intelligent Investor." Get a basic book on accounting and learn basic accounting. Pick up economics textbooks at least through "Intermediate" for both microeconomics and macroeconomics. Get William Bolstad's book "Introduction to Bayesian Statistics." You will need them for reasons that go very far beyond this post. Trust me; you want to master that book. Find a statistician and ask them to teach it to you as a special topics course. It will help you as both either a Marine officer or a Naval officer. Then after that pick up a copy of "Security Analysis." Either the 1943 copy (yes it is in print) by Benjamin Graham if you feel good about accounting, or the 1987 copy by Cottle under the Graham/Dodd imprimatur. Then, if you are still interested in cryptocurrencies and they will be blasé by then, then pick up an economics textbook on money. If I were you, I would learn about Yap money, commodity money, and prison money first, then you might understand why a cryptocurrency may not be an investment for you.