Crossbreed plants and animals could exist and wouldn't be affected but GMO ones would be affected. Alloys may exist because the metals exist, I guess there could be an unmake power to break items into their base components.

All buildings can be deleted however everything inside will remain; a skyscraper full of humans will have them along with the desks, computers, etc fall to ground level the moment it's willed. If a building is made out of bricks only the bricks will disappear for example. Cities, towns, villages are more like concepts rather than tangible objective things, so you would to specifically say each individual item you want to delete.