Even though shape of pectorals are purely genetics. Few Body Builders suggested me to do Incline Presses and Flyes for building squarer chest. Are there any scientific evidence or research to to prove this?
I don't believe there are any studies to show that those particular exercises will help build a “squarer chest” (whatever that may be). However, I think the intent of the advice was to suggest that you should introduce variation into your training routine.
A basic prerequisite for continued adaptation is variation. Performance improvements will decrease if the same exercises and training loads are continued for a prolonged period of time (AKA Accommodation). Training variations inhibit accommodation and ultimately the exhaustion stage of SAID. Polarizing training stimulus around a target response between workouts can also help recovery between workouts. These variations indirectly assists recovery since the metabolic pathway are not taxed in the exact same way every workout. As a beginner, progress can be made most every workout. Variation is inherent due to relatively rapid progress in the initial phases of training (see Initial Level of Fitness). As progress slows, subtle variations must be made in other ways for progress to continue (see variation examples below).
Without variation, you'll tend to become “stale” and gains will plateau. That includes any chance at a “squarer chest”.