Substitution PRocess

[PaREF]

While this isn't 'exactly' the same situation, it should satisfy anyone's questioning of the procedure. From the 2020-2021 NFHS casebook;

10.2.7 Situation A: Two substitutes stand and proceed as substitutues with the first entering the substitution zone. The coach quickly tells the second substituting player not to substitute this time. Ruling: If this is done quickly as not to delay the set, no violation is called.

[bob jenkins]

There is this from RefMag (the NASO supplement in the middle):

PLAY: ...two players from team B stand and approach the substitution area. B1 enters the substitution zone and B2 stands outside the zone... The second referee...authorizes B1 to enter the game. B2 then enters the substitution zone and is authorized to enter. The coach indicates that he or she does not want to make the second substitution. RULING: In all codes, once a substitution is acknowledged, the substitute may not be withdrawn without repercussion. The team should be assessed a delay sanction (administrative delay).

So, if we accept the RefMag ruling (and I recognize they are not always correct):
1) If the second sub is withdrawn before entering the sub zone, legal.
3) If the second sub is withdrawn after being authorized to enter, YUD (or equivalent)

Left open is:
2) The sub is withdrawn after entering the sub zone but before R2 authorizes entry.