That's all down to how hard you're riding. Most people will use more effort when riding IRL than riding stationary bikes.
A bicycle alone only use up space. But a human riding a bicycle will have to use force to get the bicycle to do anything, by pushing on the pedals, pulling on the handlebar ASO.
because it is fun
In the bearings and in the tires. All it does there is turn into heat - and we can't use that for going forward.
I like riding my bicycle around the house.
wear helmet, use reflectors when riding at night. always wear bright clothes. always ride WITH the flow of traffic. always walk your bike across a roadway.
Usually called "wall of death"
They're really not that common, but you can get an accessory to bikes with generator hubs that lets you power anything that can use an USB port from the generator hub while riding.
If it is an iPod Touch, yes, you can work on an iPod or use the iPod while it is charging.
It helps, by not using the car for short journeys. But we in the West need to do much more to cut fossil fuel use.
Yes, as long as it doesn't get too hot. The UV light will not hurt your iPod.
That would depend on how hard you ride, and the temperature you're riding in. If you're OK in the current temperature(whatever it is) while doing nothing much, then you will get warmer when you begin using your muscles more. And once you're warm enough you will start sweating/perspiring. No difference if the increased muscle use comes from riding a bike, jogging or whatever.