Explanation:

Under Article 1 of the Indian Constitution, the State of Jammu and Kashmir (J&K) is a constituent state of Indian Union and its Territory forms a part of the territory of India.On the other hand, Article 370 in Part XXI of the Constitution grants a special status to it.Accordingly, all the provisions of the Constitution of India do not apply to it.It is also the only state in the Indian Union which has its own separate state Constitution - the Constitution of Jammu and Kashmir.
Accession of J&K to India -

• With the end of the British paramountcy, the State of Jammu and Kashmir (J&K) became independenton 15 August 1947.
• On 20 October 1947, the Azad Kashmir Forces supported by the Pakistan army attacked the frontiers of the state.
• Due to this, the ruler of the state decided to accede the state to India.
• Accordingly, the ‘Instrument of Accession of Jammu and Kashmir to India’ was signed by Pandit Jawaharlal Nehru and Maharaja Hari Singh on 26 October 1947.