if elder is played from temporal breach and then enemy reacts flash, does that dodge the elder dragon

Yes — assuming nothing is already damaged lethally, Flash saves the units.

Elder Dragon's "when you play me" ability is a set of location-based targeting restrictions ("up to one enemy unit at each location"), and each target is checked against its own restriction as the ability resolves. Because the Dragon was played via Temporal Breach, it enters and its passive goes active immediately, but its play trigger is placed on the chain after Temporal Breach finishes resolving, so the opponent does get priority and can Flash before the trigger resolves — moving the units to base means they no longer satisfy the restriction for the location they were chosen at, so they take no damage (FAQ 9919).

The one exception: if a unit already has any damage marked on it by Elder Dragon's controller, the passive makes that lethal, and the cleanup before priority is passed kills it before Flash can ever be played (FAQ 12271). Note the moved units don't get picked up by the base instruction — that instruction locked in its own target at finalization.