Show LMS aggregate data on results slide?

1) Doing a recap on a separate slide isn't necessary -- you can just use the results layer to reshow the choices, then list the most common choices side-by-side.

2-3) The LMS is not going to do any calculating for you. It receives the data you send once the course is complete, and that's the extent of its functionality (as far as I know -- I've never heard of an LMS with this functionality). 

You'd have to determine what were the most common responses ahead of time and list them in your course manually. 

If you wanted to not use the results layer and instead use a different slide, then you'd have to preserve the user's choices. One way of doing this is setting a variable for each item that is dropped on each target. Then by evaluating those variables, you'll know which order the drag items are in. It'd be messy.