Answered: getting opponent's skyrise piece from the floor

If your opponent drops a skyrise section in the grey area, can you pick it up and place it on your own skyrise? If so, does that men you can build a skyrise taller than 7 units high, or will there just be one piece not used?

Yes, this is legal, and yes you can build a Skyrise that consists of more than 7 Skyrise Sections.