"Could you pass me the salt, please?"
Translation:Îmi dai sarea, te rog?
Not completely interchangeable as te rog is singular, va rog is plural
If you put "dai" in the first part than you are imply speaking to you singular & thus must follow the rule throughout the sentence. So "Îmi dai sarea, te rog?" I presume you could have "Îmi dati sarea, va rog?" as an alternative as that would follow the rule of a plural you being spoken to.
I am still learning too so this is what I understand of it :)