Answer : 4. "लाहौर"
Explanation :

The demand for "Poorna Swaraj" (Complete Independence) as the aim of the Indian National Congress was officially accepted during the Lahore Session of the Congress in 1929. The Lahore Session, also known as the Lahore Congress, is particularly famous for the resolution of Poorna Swaraj, which laid the foundation for the independence movement in India. The resolution was passed on December 31, 1929.