A reflector is like a clever mirror, it doesn't shine by its own but will cause any light that hits it to bounce back in the direction that it came from.
A headlight is a light, if you have it on it will shine by itself. Reflectors are great for being seen by people who are shining a light in your direction while lights can be seen by anyone looking.
Yes that's why they have reflectors on them.
motor cross is faster
I have no idea what you mean by "gear bike", so the question can't be answered.
The exact laws may differ from place to place, but usually a bicycle only require lights and reflectors if it's being used on roads/in public after dark.
Mountain bike helmets are better than dirt bike helmets
If the bicycle is road legal(has brakes, lights, reflectors) - sure.
The difference is the person who is possessing. For example you would say "I have a bike" or "He has a bike". You would not, however, say "I has a bike" or "He have a bike" unless you're ignorant and uneducated.
there is not much difference usually people think that they are smaller and are more powerful, which is true, although they can be normally sized
Depends on the type of bike. On most bikes things like locks, fenders, racks and chainguards/chaincases are optional. Lights and reflectors can also be optional.
difference between 220cc and 150cc is that 150cc has less cc than 200cc
Generally no, but the bicycle has to be properly equipped for it. This usually means a white light and a white reflector facing front, a red light and red reflector facing rear, and orange reflectors facing sideways.
The difference is that the mountain bike tube is much burlier and wider than the dirt jump tube but may not be as strong in terms of hard hitting strength.