Let me see if I can answer your questions:
1. MP3 CD burner is considered legacy because we're no longer updating it and it doesn't work with Windows 8. If you need more control over cutting up songs, you might try our newer Mixcraft software
2. You're limited to trimming roughly half of a song. The only limitation of the trial is that CD burning is no longer available after the trial is up.
3. You can control what MP3 CD Burner considers incomplete in the Audio Processing preferences.
4. To take advantage of smooth cross-fading, burn an audio CD, not an MP3 CD (unless you make everything into one big MP3) and make sure that the "Use IMAPI" option is turned off in the CD burning preferences.