Suppose a body is rotating with uniform speed i.e. dv/dt=0(all the drags and frictions are zero) then what will be the direction of torque or will it actually exist?since the only force is acting towards the center and radius and force will make angle of 0 and hence the torque will be zero
Torque is needed to speed up or slow down a spin. Here, the spinning rate is constant, so there will be no net torque. The word "net" here is extremely important. Let's say I apply $2$ $5$N forces in opposite directions. Then, there is torque, but they cancel out.
Now to angular momentum. Linear momentum $p$ is defined by $mv$, mass multiplied by velocity. Assuming the mass is non-zero, there will be momentum. One way to visualise this is to spin a heavy metal ball, using yourself at the pivot. Uponn letting go, the ball will fly. Why? Because there us momentum.