With which state the government of India succeeded in signing the 'Merger Agreement in September 1949?

Manipur

The correct answer is Option 3 - Manipur

A few days before Independence, the Maharaja of Manipur, Bodhachandra Singh, signed the Instrument of Accession with the Indian government on the assurance that the internal autonomy of Manipur would be maintained. Under the pressure of public opinion, the Maharaja held elections in Manipur in June 1948 and the state became a constitutional monarchy. Thus Manipur was the first part of India to hold an election based on universal adult franchise. In the Legislative Assembly of Manipur there were sharp differences over the question of merger of Manipur with India. While the state Congress wanted the merger, other political parties were opposed to this. The Government of India succeeded in persuading the Maharaja into signing a Merger Agreement in September 1949.