In which session of the Indian National Congress was the demand for ‘Puma Swaraj’ formalized?

The demand for ‘Purna Swaraj’ was formalized in the Lahore session of Congress in December, 1929.

Note:

After the Simon Commission of 1928, Lord Irwin offered a ‘dominion status’ to the Indian leaders. But radicals in Congress like Jawaharlal Nehru only became more determined for complete autonomy. Therefore, under Nehru’s presidency, Purna Swaraj was formalised.