With reference to Sikkim’s constitutional integration with India, consider the following statements:

1. The Thirty-fifth Amendment gave Sikkim the status of an associate State and inserted Article 2A and a new Tenth Schedule.
2. A referendum in 1975 supported the abolition of the institution of Chogyal and Sikkim’s integration as a full State.
3. The Thirty-sixth Amendment made Sikkim the twenty-second State and inserted Article 371F.
4. The Thirty-sixth Amendment retained Article 2A and the Tenth Schedule as the permanent basis of Sikkim’s relationship with India.

Which of the statements given above are correct?