If it is,then what about the pressure and velocity in a pipe having dia 10cm up to certain length and if that pipe dia is reduced linearly from 10cm to 1cm?And again from 1cm to completed closed one?

You seem to be asking about the Venturi effect, which describes how you get reduced static pressure when the velocity of the fluid is increased. This is because the increase in kinetic energy of the flid must be offset by a reductio nin pressure in order to conserve energy . The way you increase velocity in a short section of pipe is to reduce the diameter in that section. Conservation of mass flow says that velocity v must increase if cross section area A is reduced in order to keep the mass flow constant. Hence the pressure in the area of pipe that is constricted must ne less than in the rest of the pipe.

Of course if the pipe is completely closed then the fluid can't flow at all. Hence v=0 and the pressure is maximized.