can i legally download any track or acapella from this site and rebuild it on my DAW ,cut existing parts /add new and apply the sounds in other type of genres?

Hi Mark,
The ‘cc’ part of ccMixter is Creative Commons which means that each of the files (backing tracks, acapella, samples, etc) are licensed under the various Creative Commons licenses https://creativecommons.org/licenses/
You can read about it there and that should answer any questions you have about what you can and can’t do with material from this site :)

Certainly the design of this site is to use the material the CC guidelines and licenses just help to clarify the nature of the re-use! :)

Hope that helps!
Cheers,
Joel.