Rudra (Option 4), also known as Advanced Light Helicopter (ALH) Mk-IV, is an armed variant of HAL Dhruv, tailored for both utility and attack operations. It is equipped with advanced weapons systems that include a turret gun, rocket system, and air-to-air missiles. Hence, option 4, "3 only" is correct.

In contrast, the Cheetah and Chetak (Option 1 and 2) are light utility helicopters used primarily for transport, rescue, and surveillance operations. They do not possess advanced weapon systems like a turret gun, rocket system, or air-to-air missiles.

Option 1 and 3 imply that Cheetah (1) and/or Rudra (3) are equipped with the mentioned weapons, which is incorrect as only Rudra has them. Option 2, implying that only Chetak (2) has these weapon systems, is also incorrect. The passive language in the question could also confuse, but ultimately the key is knowing the different helicopters and their associated armaments.