2 -- I was not aware that changing a sky added a new camera and a new light. However, I imagine many of the library skies make use of a "sun" light, whereas the default Carrara scene uses a single "infinite" light. Basically, though, you are better off understanding the sky controls and how to custom make your own skies. 1 -- If there is a "Drop to floor" key I've never used it. You can turn on collisions (I believe they are on by default), and gently push your object down. You could even take the long way around, turn on physics, add a gravity force, then run a physics simulation. I've done that myself for an image! And then there is the question you didn't ask; Yes. You should read the manual. All of it.