| State | Description |
|---|---|
| I. Arunachal Pradesh | The capital is named after a fort, and the State has two National Parks |
| II. Nagaland | The State came into existence on the basis of a Constitutional Amendment Act |
| III. Tripura | Initially a Part ‘C’ State, it became a centrally administered territory with the reorganization of States in 1956 and later attained the status of a full-fledged State |
Explanation
Pair 1 is correct: Arunachal Pradesh’s capital is Itanagar, which is named after the historical Ita Fort ("Ita" means brick). Additionally, the state has two National Parks -- Namdapha National Park and Mouling National Park --confirming the accuracy of the description.
Pair 2 is correct. Nagaland became a full-fledged state of India on 1st December 1963 through the 13th Constitutional Amendment Act, 1962, which also inserted Article 371A into the Constitution. This article provides special provisions for the state, confirming that Nagaland came into existence via a constitutional amendment.
Pair 3 is correct. Tripura initially became a Part ‘C’ State after its merger with the Indian Union on 15 October 1949. Following the States Reorganisation Act, 1956, it was converted into a Union Territory (centrally administered). Later, it attained full statehood on 21 January 1972 under the North Eastern Areas (Reorganisation) Act, 1971, as confirmed by official sources such as the Tripura Legislative Assembly website and Sepahijala District website.