The scene where Begum Jaan and her girls are listening to Independence Day speech, on the Radio. The radio shown used to run on electricity and there was no electricity in Begum Jaan's house, every where kerosine lamps were burning, and transistor radio were commercially available only after 1954.
During the second half, where Begum Jaan and others are seen learning how to shoot the rifles, if you look closely, the rifles are all without the rear sight, making any form of aiming impossible.
During the second half, where Begum Jaan and others are seen learning how to shoot the rifles, the amount of rearward movement given to the bolt of the rifles is inadequate to extract and eject the fired cartridge or to load a fresh cartridge. Consequently no fired cartridges are ejected also.
When Ilyas and Hari Prasad visit Begum Jaan's brothel, Sujeet and Rubina were outside, lying on a rock. While they were hugging each other, it starts to rain. This scene happens concurrently with the scene where Ilyas and Hari Prasad were talking to Begum Jaan about vacating the brothel. Which means everyone at Begum Jaan's brothel should be drenched by rain. But everyone seems to be dry and not even touched by rain.
Towards the first half of the film a Shaktiman tuck is seen ferrying refugees. The said truck was manufactured only from 1959, more than ten years before the events of the film (1947).