IF 2016 presidential found invalid, what's up legally?

Let’s say it is proved that hackers from wherever actually modified vote counts in key parts of key states and tipped the electoral college vote…
Do we hold a crash election? Who’s in charge? ..Pence rode in on the same fake election result. Paul Ryan is next in line.
Do all the federal office appointments made in the past two years get invalidated? How about that Supreme Court Justice?