Can I release a single from an album or EP? Yes, you can. You can release one and the same track several times if it is on different products (a product can be a single, an ep, an album, a greatest hits album and so on).
For example, You can upload a track as a single and after a few weeks add that same track (using the same ISRC code when uploading in the app) on an EP or album. But you need to upload the complete product in the app, including the track already released. You can then decide if you want to delete the single or if you want to keep it live in stores, totally up to you as they are different products (single and EP/album).
We can't add uploaded tracks together for you and every upload in the app must be a complete upload. You cannot add or remove a track to an existing upload.