You can as long as you are careful not to overexert yourself. If your body feels good doing it then you should have no problems as long as you stretch afterwards and before as well as do a warm up before you exert yourself.
You can, but it may not be the best thing for your body if you're not in best shape. Try to include short sprint intervals into your exercise program, or try sprinting every 2 or 3 days.
You can do a sprint workout everyday but i would suggest a day off once a week. Your body needs time to recover from the tearing and breaking down of your muscles inorder to rebuild them.