Answer:
What is neither inside the house nor outside the house but a necessity for any home?
What goes up but never comes down?
In marble halls as white as milk, lined with a skin as soft as silk. Within a fountain crystal-clear. A golden apple doth appear. No doors there are to this stronghold, yet thieves break in and steal the gold.
Look into my face and I'm everybody. Scratch my back and I'm nobody.
It's the only vegetable or fruit that is never sold frozen, canned, processed, cooked, or in any other form but fresh
What do you purposefully put lots of in and on your body, but run away from when you encounter it outside?