I currently do not have any 24-bit songs, but some of the guys in the thread might be able to help you out with that.
As of the difference, I would not know, so asking someone who has used it before in the C3 thread would be advised. I do know that the C3 will only play 24-bit files if the format is WAV. Other than that, I believe 16-bit is the highest for flac.
Sorry I couldn't help you out there.