Don't really know what you mean by a jump bike...
Generally speaking a MTB is intended to be fairly versatile, and it will usually have gears enough both for slow slogs uphill, for going along the flat, and for powering downhill. Something like a dirt bike is usually adapted to run in pretty much one condition only, so taking it on a longer trail with both uphills and descents is likely to be heavy going.
not all are. if you want to do dirt jumping i recommend you do not use a normal mountain bike. get a proper dirt jump bike. i used a felt q520 xc bike to dirt jump and the forks broke and i took it in and the mechanic said i had damaged the frame and it was close to snapping.
you sit on it and push the pedals around in a circle like a rode bike but is off road .
Use the Acro Bike to pass the straight white lines to pass gaps use the bike jump technique.
use acro bike
Yes you can.
Yes, if you can find the correct bottom bracket for the frame.
use your bike but press b when you are on.
Use the skilift
Use an acro bike and jump onto it
Use the Acro bike to get across when there is a gap in the lane do a sideways bike jump to get across.
It's a saddle. Some are sold as MTB-specific, but unless you plan on doing jump and drops you can use whichever fits - regardless if it's "road", MTB, or even BMX.
just use the keys on keyboard (b+up=jump up, b+down=jump down.