Tiny modification to an existing small Wordpress plugin

Hello. I have a simple wordpress plugin which allows me to upload files for users through the normal wordpress admin panel. Then the users can login from the front end of the website and download the files which are associated with them. I need two modifications to this plugin. A) Display the upload date of the file in the table in this format: 2008/09/26 - and list them by default in the most recent at the top. B) The problem is that some users need different user accounts but the same file. If I upload one file and select it for more users and then delete it, it’s not possible to delete it for the other user anymore because it gives an error that the file was already deleted. Multiple users should be allowed access to the same file, and can be independently deleted without it breaking it for the other users.