Answer:
I am the building with the most number of stories. What am I?
What has many keys but can't open a single lock?
Though I am only two words I have thousands of letters in me
Good memory, skin like the sea. A great beast I am, yet vermin frightens me. What am I?
I am rarely touched but often held and if you are smart you'll use me well.
Whoever made me don't want me. Whoever bought me don't need me. Whoever use me don't know me.