That's not so easy to answer, as there's no guarantee that the bike still has the original tires. If it has any tires on it's usually printed on the tire sidewall what size it is. I'll post a link with info on rim / tire combos.
no.
If it's a road bike it's probably the approximate width of the tire.
It helps to cushion the rider against the uneven road surface !
Can be a road bike, a Tri bike, a TT bike or a track bike.
MAYBE - , frame size has nothing to do with tire size. Style does, and if its a mountain bike, it will not work with a 27 (road racing) wheel and tire. Brakes will not fit.
Someone can purchase bike tires for road use from Canadian Tire. They have knowledgeable staff that are able to help you with your purchases. Their information is excellent.
It depends what use the bicycle is put to, it may be a racer, a road going tourer or an off-road mountain or trail bike. All have very different tires.
If the bike is set up properly, with a real fixed hub, then you should be able to do it. Keep in mind that the contact patch on a road bike is quite small, and that you're likely to wear your tire out quickly.
Can be quite a difference there, from 400-500 grams for an XC tire to almost a kilo for a wide DH tire. Narrow road bike tires can be even lighter.
If you think about the part that prevents the tires from throwing mud and road grime onto the bike and rider they're called fenders.
No. Maintain the pressure stated on the side wall of the tire.
Typically the air pressure for a road king or touring bike is 40 PSI look on the tire itself and it will give a recommended tie pressure. Ride Safe