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.
Mountain bike helmets are better than dirt bike helmets
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.
If the bicycle is road legal(has brakes, lights, reflectors) - sure.
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
difference between 220cc and 150cc is that 150cc has less cc than 200cc
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.
The main difference between 28 and 700c bike tires is their width. 28 tires are typically narrower than 700c tires, which are wider. This difference in width can affect the overall performance and handling of the bike.
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.