Hey Ganesh

Public Prosecutors and Legal advisors are different. Public prosectors are the lawyers who conduct the case on the behalf of the government. They represent the state in cases of a criminal trial.

Whereas Legal advisors are not the same as public prosecutors. They can be appointed by private companies, MNCs, firms, organisations, government organisations or departments for the purpose of advising or representing  on various legal matters.

You do not need to be a public prosecutor in order to be selected/ employed as a legal advisor. Different organisations have different criteria for selection which maybe specialisation in an area of law or some minimum years of practice etc depending on the job profile.