How to unhide files on Mac? I did: chflags hidden /Users/MyUser/Library/(theareawheremyfileis) and it hid my file.
I did this in Terminal, now I typed in ... unhidden ... and I can't seem a way to unhide the file I hid.

Along with that, I want a way to see all hidden files just using a terminal command, no matter hidden by the computer or hidden by the user using chflags.

So I need two different things.
chflags nohidden will unhide a hidden file/folder.

You can press Command+Shift+. to show all files regardless of any other state (in macOS Sierra and above.)

Alternatively, you can run the command defaults write com.apple.Finder AppleShowAllFiles true then relaunch Finder (any version of macOS.)