Starlight Road: Suppose that "Elemental Hero Absolute Zero" is returned from the field to the Extra Deck and its effect activates. If you Chain "Starlight Road" to the effect, then the effect is negated and the "Elemental Hero Absolute Zero" in the Extra Deck is destroyed. Also, you can then use the effect of "Starlight Road" to Special Summon "Stardust Dragon".
Starlight Road: Suppose that "Elemental Hero Absolute Zero" is sent to the Graveyard or is removed from play, and that its effect activates. "Starlight Road" can be Chained to negate the effect, but "Starlight Road" cannot destroy "Elemental Hero Absolute Zero", so afterwards you cannot Special Summon "Stardust Dragon".
Starlight Road: Suppose that "Elemental Hero Absolute Zero" is sent to the Graveyard or is removed from play, and that its effect activates. "Starlight Road" can be Chained to negate the effect, but "Starlight Road" cannot destroy "Elemental Hero Absolute Zero", so afterwards you cannot Special Summon "Stardust Dragon".