Q1) What is the main notion of Death of a Salesman , your answer should be ?related with Great Depression Era

This play takes place in the 1950's so I'm not sure what you mean by "Depression Era". Death of a Salesman premiered in 1949 on the brink of the 1950s, a decade of unprecedented consumerism and technical advances in America. Many innovations applied specifically to the home: it was in the 50s that the TV and the washing machine became common household objects. Miller expresses an ambivalence toward modern objects and the modern mindset. Although Willy Loman is a deeply flawed character, there is something compelling about his nostalgia. Modernity accounts for the obsolescence of Willy Loman's career - traveling salesmen are rapidly becoming out-of-date. Significantly, Willy reaches for modern objects, the car and the gas heater, to assist him in his suicide attempts.