You can right click or command click on any image and choose "Go to Folder in Library" to get to know which folder is it stored in.
Duplicates are imported in Lightroom only when you have the option "Do not import suspected duplicates" unchecked at the time of import.
If you had it unchecked, you would probably have to search for a particular filename to see if there is a single copy for it or multiple.
Thank you. That brings me to the folder location. However, I should have phrased it better. I mean which collection I placed the photo in, if I placed it anywhere at all.
For collection, you can choose Go to collection.
If it would be a part of any collection, it would list the name of that particular collection and if not, it would say "not in any collections"