what is the actual range of airport extreme in meters ? can it cover my whole home if it is in the range of 50 meters of radius ?

Most likely depending on if the walls of your house is brick or no brick. You may need to add a airport express as a expander if your walls are brick

What is the actual range of the Airport Extreme in Metres? Can it Cover up to 50m in Radius?

50m would be approximately the range.....if there were no walls or obstructions in the path the wireless signal must travel.

Since we know nothing about how many walls, ceilings or other obstructions there might be the path that the wireless signal would take in your home, or the construction type of those obstructions, we cannot even make a guess about whether the AirPort Extreme might provide a signal to cover your home.