Does a 4 Wheeler go atleast 50 miles Per Hour?

Many will. Some 250cc quads will get there. All 350 and 400cc and above will exceed 50 mph - 400's can reach 65 or so, 450's and 660/700's - 75 to 80. I am describing SPORT quads here... utility quads are usually somewhat slower, but the large displacement machines will all exceed 50 mph by a wide margin.