Can i attach the downloaded audio preview file with after effects project file zip?
No. You can use them in your preview video if you credit the author of the track, but you can;t include the preview file in your main zip file.
How can i use a audio preview file to after projects when its come 2 or more track versions together?
check this track - http://audiojungle.net/item/aspiration/14505819?s_phrase=&s_rank=3
there have 3 versions. Problem is when i use one of them with audio track edit, how can i arrange the audio track composition for buyer?
Make an ‘Add audio track here’ comp, then cut up the comp rather than cutting up the track. Hide it and lock it in your main comp so it doesn’t get messed up and then the buyer just needs to buy the track and drag it into the comp. Obviously mention that in our instructions.