Yes, It also builds muscle.
Yes, one of the best.
any excercise is good of course, I swim a lot. I watched a BBC programme the other day, 3 minutes really hard to near exhaustion riding on a static fitness bike once a week really does burn of fat, the internal stuff too, but then one should also eat in a healthy manner too. so that would be 12 minutes a month. I haven't checked to find it on the internet as yet, but I will. I ride my normal bike everyday anyhow and really power up hills etc.
Not in my experience.. it IS a very good cardio-vascular workout and is excellent for muscle toning, but for real fat burning you can't beat running, hiking or serious cycling (the uphill kind).