"Swearing in" does not make one President. You have to be qualified, win the majority of the electoral vote, take the oath, and wait until noon on January 20th following the elections. If you don't satisfy all of the above, you aren't President.
The Constitution doesn't even require a "swearing in" ceremony, let alone say who shall conduct it. I could take the oath right now, by writing it out on the back of old pin-up calender, and signing it. Would that make me President? I don't think so.
Yes, the occupant of the oval office is entitled to due process, but only a President, or other legitimate office holder, can be impeached.
Wrong Of course it does. See Article II Section 1. The last paragraph even specifies the words of the oath. I sense that you may not be credible talking about the US Constitution if you do not know that...
So. actually you admit what I wrote is correct.
And you are wrong about only a President being vulnerable to impeachment. Many federal judges have been impeached by the US Congress. The only penalty if convicted in an impeachment is removal from office. Once removed though, other charges may be made by prosecutors.
See de facto officer doctrine.