How dominance is decided ? Explain

The law of dominance is used to explain

How is NOT gate realised? Explain.

How do "Pleiotropy", 'incomplete dominance", "co-dominance" and "polygenic inheritance" deviate from the observation made by Mendel ? Explain with the help of one example for each.

What is codominance ? Explain it with suitable example. How does it differ from incomplete dominance?