Drag & Drop Layers

I have a drag and drop activity created, and I’m wondering if I can fix the layering of the draggable items. Currently when you drag one of the items on the top, that item goes underneath the other items. I’d like for selected draggable item to always be on top of the rest of the items … how can I do this?

Also another quick question - is it possible that once an item has been dropped into a target area, that if they try to drag another item in that same spot, it will just go back to its original postion - because it is occupied?

Thanks …