2. I'm not asking you to tell me which crypto to invest in, just curious what your opinion is.
So what answers do you really expect? We cannot offer what choice of crypto we can suggest but we should tell where we should put it?

If I have that amount I would put it with ____ and wait until it pumps. See, that's difficult to answer.
Anyway, I'll look into altcoins (NFT, DeFi) that are cheap if I have the amount since Bitcoin had been expensive and it may take long before it will be dumped again, or not.
I think you could try something like "If I had something like that I would diversify it and put it on many things in crypto and many things outside of crypto" and that would make sense, you are not giving any names, like saying "I will buy a house" and that doesn't say which house. I personally would be super rich if I had 4 million dollars, in my nation that's so much that I could live a very luxury life and still would not have to make more profit, like 4 millions do not need to be invested and go bigger if I want to live with that forever, I could just live with it without earning 1 more profit.
However just to make sure I will probably buy a business building, those do worth a lot here, usually they are like 4 stories tall or maybe 3 to 5 in some places but 3 story is too small and 5 is usually too expensive. I will get a 4 story tall one and probably a very modern looking one, get the inside done very professionally (not the items but the buildings inside) and just rent that out to companies, that would yield at least 20k per month easily, and I can live with that without spending any other dime, I could get like maybe 2 of these, that means I could actually get super rich.
I know it is not crypto related but why must it be crypto related, then I could use the income to buy more crypto anyway because I will make more than I could spend, I am not making 20k in a year now so making that in a month will allow me to go back into crypto.