Well, if you offered to pay me enough I'd be quite happy to sell you a rim with a tire mounted on it. Odds are it'd be quite useless though. 99% of all tires need a tube inside them to hold air, and 99% of all rims can't be mounted to a hub (with the spokes and all that) with the tire in place.
But I'm guessing that what you really want to know if you can buy a wheel that is ready-to-roll. And sure, but you'll either have to go to a bicycle store, pick your wheel, tube and tire and wait while they mount it up for you, or buy something used off Craigslist, eBay or similar. They often sell complete wheels.
Probably, yes. There are some recommendations on rim width vs tire width - I'll post a link. You have to scroll down a bit.
Of course you can.
Sure, in terms of width tires aren't that picky about which rim they're mounted on, there are far more tire widths that there are rim widths. Read here for more: http://sheldonbrown.com/tire-sizing.html Do note that the frame might not have enough clearance for a wider tire though.
The rim will be down against the ground
Tires off the rim, or the tire and rim off the bike?
Can be a road bike, a Tri bike, a TT bike or a track bike.
2.35 is the width measurement, which is only half the story. There's diametertoo. And unless you get the diameter spot on, the tire won't fit.And normal doesn't cut it, there are plenty of normal rim sizes. You have to be specific.Rims can usually take tires of quite different widths, but the tire has to clear the frame too. And 2.35 is quite wide. My bike can't run it.
The air pressure inflates the tire and holds it away from the rim.
Exactly the same way you remove a car tire from its rim. Everything's just bigger.
Take the tire and the rim to a tire shop. It requires special equipment to properly replace the tire and balance the rim.
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.
Deflate tube, pinch tire inwards so that the bead loosens from the rim. Use a tire iron/tire lever to lift one edge of the tire over the lip of rim. Work your way around. Once one lip is off the other can usually be pulled off by sheer force. There's bound to be a nice video about on Bicycle Tutor, see link below.