Is this presidency or president? Because Joe Biden and Donald Trump are not options to be the 50th president, but could (theoretically, however unlikely) be the 50th presidency.

@SamVrana Presidencies, I guess? I will go by the wikipedia list of US presidents and the generally accepted numbering system, by which Biden is the 46th. This is the system in which Cleveland is both the 22nd and 24th President having served non-consecutive terms. Anyone please comment if you think this is incorrect/unreasonable.

@WXTJ Thanks!

Is "Nobody" potentially a valid answer to these questions? Or do they resolve N/A if there is no Nth President?

@StevenK 'Nobody' is a valid answer in my opinion. If the USA no longer exists in its current form (subjective judgement by me), or the office of President no longer exists (eg change in political system to a monarchy...) I will choose it as the correct answer, if somebody has entered it. If nobody has entered it, I will resolve n/a.

If the election result is disputed and in my opinion (relatively distant and unbiased) it really is unclear, I will wait until a clear consensus emerges. If not, I will choose 'nobody' (if entered) or n/a (if not).