Bases loaded (or R1 and R3), 1 out. R1 and R3 both leave early on a line drive or fly ball to the right side of the field (for this hypothetical so that the logical play is to appeal R1 leaving early). If R3 scores before the appeal on R1 is upheld, does the run count?
Followup, since a play has been made at first, can the defense still get the "4th out" by appealling R3 leaving early?
The appeal on R1 is a time play. R3 probably scores.
The appeal at 1B is NOT a play, so the defense can then appeal on R3 for the advantageous fourth out. If upheld, the run would not score.