Clarification sought on citizenship

The part II of the Constitution of India i.e., article 5-11 doesn't define any statute about citizenship for anyone migrating from British protectorate of Sikkim, and which was under the British Suzerainty then, which was part of India as defined in the Government of India Act, 1935 (as originally enacted) (Chapter II, Interpretations, Provision 311), to India, before and after the temporary Standstill agreement of 27th of February 1948, just before and after the commencement of the Constitution of India on 26th of January 1950, just before and after the Indo-Sikkim treaty of Dec 1950 when Sikkim became a protectorate of India, just before and after Sikkim became an associate state of India in 1974 under the Constitution (35th Amendment) Act, 1974, just before and after Sikkim officially became the 22nd full-fledged state of the Indian Union on May 16, 1975 under the Constitution (36th Amendment) Act, 1975 which repealed the 35th Amendment. So what shall happen about the legal status for such persons and legality of any business conducted by such persons residing in India, during the various stages of integration.