I'm assuming you're asking about how to remove the freewheel, as the Mongoose Rebel 20 is a single-gear BMX. In that case you need the correct freewheel puller to get the freewheel off. Check out www.parktools.com for more info.
Depends on how fast you pedal. As it is a single gear bike. BMX bikes are made that way because if crashed, the bike would be 10 times harder to fix.
This bike has a six speed gear box, so six gears.
Depends on if it's a freewheel or a freehub design. For a freewheel you need the appropriate freewheel puller. For a freehub you need a splined lockring tool.
On the left side of the bike, just behind the crank case and the left foot peg, is the linkage for the gear shifter. It's held in place by a 10mm bolt. Remove the bolt, remove the linkage, and replace at the desired angle.
I have no idea what you mean by "gear bike", so the question can't be answered.
Top Gear Hyper Bike happened in 2000.
Yes
no dirt bike gear is just a helmet and jacket, but paintball gear is a helmet a paintball gun and padding
Top Gear Hyper Bike was created on 2000-03-07.
Pick a gear that gives you the right ratio, then go for it. No difference than from a single-speed bike.
being in top gear means you cant shift no more and means your going fast as your bike will allow and by bottom gear you mean low gear which means your in lowest gear possible.
That's pretty much dependent on your strength and your pedalling skills. You are the motor, your ability is what decides how fast the bike is. If the rider is immensely strong, the fastest gear is when you have the chain on a big chainwheel in front, and on a small sprocket at the rear. But for someone of normal strength, the fastest gear is one where you're strong enough to keep turning the cranks at about 100 turns/minute.