

You can only pardon someone who was convicted of a crime.
I don’t believe that’s true. See the pardon of Richard Nixon, who was never even impeached, let alone charged. I believe there’s some debate on the validity of such a pardon, but none (including Nixon’s pardon) have been challenged in court.
Oddly enough, that convention isn’t universal. Top-to-bottom is typical in the US, UK, and Commonwealth, while bottom-to-top is common in continental Europe and non-anglophone Americas.