I don’t want to spoil your party, but some of these statements are incorrect.
I’ll focus on one that kinda feeds through to all the other statements.
You can reduce risk by owning positively correlated stocks as well, so any combination of stocks can lower idiosyncratic (unsystematic) risk as long as they are not perfectly positively correlated (which is impossible in practice).
If you want to see it in action, there’s apps like this one: Two Asset Portfolio Calculator