if you are seeing photos in several albums, the versions in the albums are no duplicates. Photos is storing each photo only once. when you add a photo to an album, the album is just referencing the one copy in your photos library. For example, if you have a photo showing dog playing with your cat, you can add the photo to the album "My Dog" and to the album "My Cat" with creating a duplicate. You hav only true duplicates, if you are seeing the same photo twice in the All Photos album side-by-side or in the Moments side-beside. Albums are just different view of your photos library, grouping your photos according to different criteria for easy access.
The "trash" button is behaving differently, depending on whether you are using it while viewing an album you created yourself or in the main, predefined Photos view.
- If you are selecting a photo in one of the predefined main views, created by Photos for you, you have only the option "Delete" when you tap the Trash. Clicking "Delete" will move the photo to "recently Deleted" and it will vanish from all albums.
- But when you are viewing an album you created yourself and select a photo and click the trash bin button, you should be seeing two options: "Remove from Album" or "Delete". The "Remove" option will just remove the photo from the album you are viewing and the photo will remain in all other albums. Tapping "delete" will move the photo to "Recently Deleted", just like in the main Photos view.