You're probably thinking of the rotor/gyro/detangler, the thingy that allows you to do a barspin w/o getting your brake wires all messed up.
A Threaded headset.
The headset is a set of bearings that allows the fork to turn smoothly in the head tube of the frame w/o sticking wobbling around when you turn the handle bars.
the fork gyro (if have) and stem and mostly important the headset
A female BMX rider is called a Betty.
Yes
Next - 2005 BMX Games 5-8 was released on: USA: 2007
The only thing on a BMX regularly called a spindle would be the crank axle. Although I suppose one could use spindle for the pedals and the wheel axles as well.
Bicycles don't have head gaskets, the closest thing is the headset, the bearing between the fork and the head tube of the frame. www.bicycletutor.com, www.sheldonbrown.com and www.parktool.com are good sites to read up what's wrong and what to do about it.
Yes its very fun.
yes
There are MTBs with 20" and 24" wheels for smaller riders, which probably is the closest thing to what you're describing. These wouldn't be BMX bicycles though, since BMX bikes don't have gears and have a taller handlebar than a mountain bike.
it matters what you are going to use it for