Rana saab has a daydream about meeting his long-lost wife and subsequent confrontation with Inpsector Shankar. However, at that point in the film, Rana saab had never met Inspector Shankar before so he couldn't have known that he was a police officer and that he was investigating him. Rana saab actually first meets Inspector Shankar immediately after the daydream scene.
The character played by Parveen Babi is raised by Amit, however as the film progress she meets a police officer (Shankar) who is the exact duplicate of Amit's likeness. Her character is unable distinguish the identical likeness of the two characters so she never brings this to attention to Amit.
In the song "Asli Kya Hai Naqli Kya Hai", in the latter part of the song, there was a editing error where it showed a gap between both Amitabh Bachchan's characters.
Actually, Rana Sahab had picked up Shankar's identification card from the floor at the airport, read it. He realized he was an inspector, and presumed he was investigating him, therefore he dreaded meeting him.
It was revealed by Waheeda Rahman to Amitabh Bachchan (Shankar) when Parveen Babi was arrested that the two of them had been in contact for months. Waheeda Rahman's character is of a national award artist, recognised throughout the world and Asia. Parveen Babi was coming to India to have a statue of her late father made by Waheeda Rahman. Parveen Babi never mentioned to her adoptive uncle (Amitabh Bachchan, the older character who was Waheeda Rahman's husband) who she was getting the statue made by. At that point in the movie the older Amitabh Bachchan considered his pregnant wife dead.