A "full song" should be clear. It's the version thats properly mixed and ready for release.
While mixing the song, you are arranging every bit and peace to where it belongs.
Otherwise vocals or instruments may end up at the wrong time stamp.
You may also add different audio effects.
Then you get something like this:
Listen how the BG and lead vocals don't fit the beat? It's out of tune and sounds horrible.
The unmixed stems have NO time stamp. They have NO place to be and NO audio effects.
They are pretty much useless unless you start arranging them properly and make a song out of it, that sounds good.
That's it for now on infos about completed music. Maybe, if I get around and motivated again, I'll let you know.