Generally incomplete files will have a number in front of them; eg: T-4226821-artist & title

So you should avoid those.

If you got an incomplete song, there's a chance it was recorded from radio or something. I don't know why people share those but that might explain why there's parts missing: edited out the DJ intro, etc.

The reason sharing of incomplete can be a bonus is b/c the part that is complete can help speed up downlding for other people.

By the way there's no need to mention the actual file-name when giving an example.