In a transformer, what is the phase difference b/w secondary induced voltage and current in secondary circuit for purely resistive load?
With a pure resistor connected directly to a winding, the current through the resistor and the winding are equal. The voltages across the resistor and the winding are equal. (Either the voltage or the current may be viewed as opposite in sign.) There is no phase difference between the voltage and current on a pure resistor. Therefore there is no phase difference on the winding (from the perspective of a source).

You reasoning is for an inductor not a transformer. For example, an ideal transformer is assumed to have infinite inductance and develop zero net flux. Regardless of whether the transformer is ideal or not, the relationships in the first paragraph hold and is the easy way to answer your main question.