making Subs/Functions private to .tBasicU-file?

[ReneMiner]

I want to create some additional Unit-Files with some subs that should only be accessable to the particular unit-file itself. So I would write for example

Private Sub mySub()
'...
End Sub

but help does not tell anything about keyword Private even though it gets colored blue and capitalized in the script.

So I want to make sure: can just variables be private properties to the unit-file or are subs and functions also allowed?

Can two different unit-files have the same titled private subs/functions also?

And some additional small question:
Can a function call itself (recursive)?