Explanations:
Sikkim was conferred the status of an associate state of Indian Union in 1975 by the 35th Constitutional Amendment 1974, while Sikkim was granted full statehood by the 36th Constitutional Amendment 1975. In a special referendum held in 1975, more than 97 percent of the electorate voted for the merger of Sikkim with India. Sikkim became the 22nd state of India on May 16, 1975.