just throw it in the garbage
very carfully with a soft damp cloth. If the disk is badly scratched, you should take it to a place that has a CD buffer that can get rid of most scratches.
you cant
You can't
a CD does not need a case for it to work. if the CD has scratches then it wont work
Not really, but dish detergent and glass cleaner are good for getting smudges and dust off. you should try that and see if it works.
Sell it!
It is impossible to completely remove scratches from a CD. Many commercial products to remove scratches exist, but they can often exacerbate the problem. You can "buff" out scratches by rubbing a small amount of fluoride toothpaste on it in a circular pattern.
no
take it to a video shop :)
Yes it does
They can make it skip or not play.
It means better quality and more resistant to scratches, and those are the best Cd's