I want to know regarding procedure of FIR filing in a police station.

What is the exact process of FIR? I am learning few things related to law and i want to know few things related to FIR. 1. Do police file FIR directly if some person approaches the police station and asks them to file a FIR? 2. Is it possible that a person approach the police intention to defame someone and write a FIR against him just to make his/her record bad, even if the person has not committed any crime? 3. Is it possible that police while writing a FIR makes a mistake and write someone else name as an accuse, lets say if police was about to write a FIR against Sanjay Singh and by mistake it writes Sanjay Vyas? 4. When a police catches a criminal then whether is it possible that police while registering the FIR, the criminal doesnt tell his name rather he pretends to be someone else? For example if police catches a person Kapil in drink & drive case, takes him to police station and asks name of criminal and he tells the police that his name is Dinesh along with fake ID of Dinesh?