4.
You can assert a fifth amendment privilege and not testify. But if you go in and swear to tell the truth, then you better do it. Otherwise, if a prosecutor finds that you have testified in a way that is factually incorrect and you had reason to know that it was factually incorrect, then you're guilty of perjury.
Richard Ben-Veniste
5.
You do not have to incriminate yourself. But once you assert your innocence, and once you say you didn't do anything wrong, you can't then use the Fifth Amendment to say, 'I'm not answering questions.'
Rush Limbaugh