Can we also use conjugate of Voltage (V*) for measurement of Complex Power?
Mathematically it's true (with a sign difference, as jonk mentions in the comments), but practically, V is used as the reference, while I will lead or lag in relation to V. Therefore φ is attached to I, rather than V, so even if the voltage is V∠θ and the current I∠γ, θ is considered the reference, and thus the result is a function of the difference of angles, φ=θ-γ. If I was the reference, then IV* would be used.