I redownloaded the osu! Catalina build, but this time, it told me that '"osu!" is damaged and can't be opened. You should move it to the Trash." So I deleted this new version and tried to reopen the first version that I downloaded.
Using this first version, I tried manually installing the .NET Framework using your steps, but it gave me another error. The following pastebin link has the error messages and information you requested in your reply.
https://pastebin.com/GMbyJETa
Using this first version, I tried manually installing the .NET Framework using your steps, but it gave me another error. The following pastebin link has the error messages and information you requested in your reply.
https://pastebin.com/GMbyJETa