The correct option is "1 and 3 only" because, as the Chief of Defence Staff (CDS), the individual serves as the Permanent Chairman of the Chiefs of Staff Committee, facilitating coordination among the three armed services. Additionally, the CDS acts as the Principal Military Advisor to the Defence Minister on tri-service matters, thereby ensuring cohesive military strategy and policy. However, the CDS does not exercise military command over the three service chiefs, as they retain operational control within their respective branches; thus, option 2 is inaccurate. This distinction is crucial in understanding the CDS's role in promoting jointness and integration within the Indian Armed Forces, aligning with defense modernization and strategic objectives.