Only Scenario B specifically prohibits the Infinity Gauntlet or the Infinity Stones from being used. Which means in Scenarios A and C the Infinity Stones on the Gauntlet that Tony Stark made is in play since it was in possession of the Avengers when the hero army arrived.
So in Scenario A whatever heroes are durable enough to withstand the initial shockwave attack can potentially grab the Gauntlet and Snap Ashorc into dust. In Scenario C the Flash can grab the Gauntlet and Snap before Blowstone gets to attack.