The ATK increase of “Skyscraper” is a Continuous Effect and does not start a chain.
If “Skyscraper” is on the field and you attack a Defense Position monster with an “Elemental Hero” that has ATK lower than the ATK of the Defense Position monster, the “Elemental Hero” gains +1000 ATK even though it was attacking a Defense Position monster.
If your opponent’s monster’s ATK is increased during the damage step, like “Injection Fairy Lily” or “Covering Fire”, your “Elemental Hero” will gain the +1000 ATK for “Skyscraper”.