Strategic. Long-ranged missiles and a high-powered radar, it's for protecting critical targets, military and civilian.
People will tell you the system is mobile, and it can move, but it's not a high-mobility air defense system that can shoot while moving, like NASAMS can:
S-400 is a big, cumbersome weapon systems that combines a lot of parts that need time to setup, warmup, sweep for targets and then engage them.
These S-400 batteries have been setup in Syria following the incident with Turkey:
A lot of stock. Russia does two things very well. Missiles and electronic warfare, offense and defense. The US considers this to be one of the most threatening SAM systems on Earth.
Also a lot
. Because nations recognize this is a threatening platform and are or have developed hardkill and softkill countermeasures to defeat it. It's susceptible to electronic attack, and it can be overwhelmed too by decoys, jammers, chaff countermeasures, saturation attacks by drones, artillery and rocket fire... there's a lot of ways it can be overwhelmed.
But the S-400 launchers aren't alone. In this photo, also of an S-400 battery in Syria, we can see a Pantsir S-1 that has been deployed alongside S-400. It's job is to defeat rocket, artillery and mortar fire, and low-flying aircraft like UAVs or attack jets and helicopters.
We recognize S-400 is a threat, and they recognize we can threaten S-400. Both sides have measures to lessen the effectiveness of the other's measures and countermeasures.
I don't follow Indian missile defense systems too closely, so I can't answer the question pertaining to domestic projects or developments, but I can answer the first part and the answer is "No".
Unless you're buying Chinese variants, there's nothing on the market that can provide the same capabilities in a land-based system.
For naval SAMS, it's a different story, but SAM development in outside of Russia and China is mainly centered around short-to-medium ranged anti-aircraft missiles like surface launched AMRAAM (See NASAMS) or ESSM and SAMP/T or ballistic missile defense like the medium range MEADS:
And longer ranged THAAD:
Neither MEADS nor THAAD are very capable against aircraft. And SAMP/T, NASAMS and comparable missiles lack range and don't perform well against missile threats.
S-400 combines a bit of both. Capable and long-range anti-aircraft and short-range, and less competent anti-missile capabilities.
That depends on where it's being put. How far can the radar see? Are there obstructions that can mask an hostile force in the distance that would obscure targeting or confuse a radar operator, like mountains or trees? Is the missile system on a hill or in a valley that would hamper its sensors ability to track and identify targets at greater ranges.
What altitude is the missile system at? Different altitudes lead to different performances by the missile, same with humidity or dry air.
The Earth's not flat or uniform and there's a lot that can affect the missile and sensors performance.
You'll see all sorts of maps, promotional photos, posts and claims of S-400's 400km ranges.
But that's not realistic given, plus only one missile in an S-400 system has that range and it's for intercepting large aircraft like heavy bombers or AWACS platforms.
It'll hamper the effectiveness of Pakistani cruise missiles and aircraft, even over Pakistani airspace. It's a potent weapon system that can't be downplayed.
Will it change the military balance? I never suggest anything can because for every system there's an antidote to foil it, but it shouldn't be underestimated or brushed off either.
It's no wonder weapon, as many are extoled here on PDF but certain members of certain nationalities, but it's a damn fine piece of kit too.