Which Act is not the landmark in the development of the Constitution during the British Rule?

The Protection of Civil Rights Act, 1955, is a post-independence legislation enacted by the Parliament of sovereign India to prescribe punishment for the practice of untouchability. In contrast, the Regulating Act of 1773, the Charter Act of 1833, and the Government of India Act of 1919 were key legislative milestones introduced under British rule that shaped India's constitutional history.