
Nuclear deterrents exist, but one cannot say for certain how effective they are until a nuclear attack occurs. India’s DRDO has a program called the Ballistic Missile Defense (BMD) system, which has been developing deterrents as part of a holistic defensive strategy.
That’s not how missile defense systems work. Missile deterrents are surface vehicles equipped with radar and their own missile systems. The radar detects, within its range, incoming missiles, drones, or jets and launches a missile to neutralize the target.
India is currently using the Russian-made S-400 which has a range of ~450km.
Edit: Sorry, I misread your comment because I’m quite sleepy. We’re talking about the same systems. Missile defense systems are also known as deterrents, as they deter incoming missiles from hitting their intended targets.