While simulating Parallel RL Circuit with ideal Inductor excited by the 50 Hz AC source, why the current through the inductor is unidirectional, because of which the reactive power frequency is only 50Hz rather than the normal 100Hz

The current through the (ideal) inductor is the voltage across the inductor integrated over time. If your voltage is an AC source without phase shift the voltage is 0 at t=0. If the initial current through the inductor is set to 0 then the result of the integration is always >= 0. The resistor has no influence on the inductor current.

If this doesn’t match your expectations you can modify the initial current through the inductor or the phase shift of the voltage source (e.g. set the phase shift to 90º where you’d expect the current to reach 0).

Thank you sir, you were spot on.