So let me ask you this as well: how do jammers work?
There are two main categories of interference: active and passive.
Active interference is exactly that -- active. The countermeasures contains sustained energy levels. Examples are dedicated platforms like the EF-111 and EA-6 aircrafts, and 'jammer' pods. Active interference is controllable, meaning they can be focused and their energy outputs are flexible as needed to exclude certain parties like friendlies in the immediate area.
Passive interference is essentially chaff that merely reflect. The energy outputs are usually omnidirectional and loses strength over time and range.
Countermeasure interference signals -- regardless of method -- do not need to overpower the transmitted signals. A simple example is listening to music on the radio. The intention is to enjoy a
CONTINUOUS stream of a song, which is a finite container of musical notes unique to that song. Obviously, a song from Brittney Spears is different than a song from Wolfgang Mozart. Interference signals -- intentional or accidental -- disrupt that enjoyment. The sources of the interference can come from bolt of lightning, a stray signal from a passing aircraft, or reflections from buildings.
For this discussion, a seeking radar is 'enjoying' a continuous stream of reflected signals reflected from a target. The longer the duration, the more secure the seeking radar in determination that there is a body in front.
Active countermeasure
DESTROYS the integrity of that data processing of that signal stream.
Passive countermeasure
DEGRADES the integrity of that data processing of that signal stream.
The difference is significant in that tactical situations generated the need to design dedicated countermeasure platforms like the 'E' versions of current platforms. No different than there are 'strike' or 'attack' or 'superiority' versions of the base platform to suit different tactical situations.
In attacking a ground target that is defended by a network of air defense missile stations, dispensing chaff is not a viable option. The air defense network produces high EM traffic and not only that, that traffic is often coordinated because each transmission come from a different source location. A chaff cloud always loses altitude and its mass integrity can be affected by local weather condition, so it loses efficacy quickly. An attacking force would be foolish to rely on passive countermeasure alone, such a plan would be a desperate plan of final resort.
So can the SU pilot apart from releasing countermeasures like chaff, decoys can an aircraft actually jam a missile like an AMRAAM?
A 'decoy' is a seduction/distraction method.
A chaff cloud can be a decoy in the sense that momentarily, the combined effects of individual chaff strings presented a more attractive EM alternative than the target. But a decoy is usually a more EM structurally coherent method
OVER TIME. This is a crucial difference. A gust of wind will affect the physical mass of a chaff cloud but will do nothing to the physical structure of an antenna. So with these choices, a seeker will focus on the steady EM state of the antenna.
A fighter is unlikely to carry something larger like a decoy which should be constantly powered to maintain that steady EM state.
What is the effectiveness of firing multiple missiles at one target at an interval? does it even work that way?
Realistically -- no.
What is that interval? What is the missile to start?
A radar guided missile have a different intercept program than an IR guided missile.
A starting point for the interested layman are the navigation laws and one of them is 'proportional navigation'...
https://en.wikipedia.org/wiki/Proportional_navigation
...Then there is the 'pursuit navigation'...
https://en.wikipedia.org/wiki/Pursuit_guidance
Radar guidance is predictive, meaning base upon programming sophistication, the radar system can give target speculative locations (plural) in continuous time-space calculations. That is usually proportional navigation.
Pursuit navigation is much more simplistic and based upon sensor capabilities. An IR sensor is passive and do not provide much target information other than an IR tensity in contrast to background. If that IR intensity moves, the sensor follows. Hence, the word 'pursuit'.
So based upon this knowledge alone, launching multiple missiles at a moving target is already problematic. Not impossible, just problematic. A radar guided missile maybe focusing on the previous missile instead of the target. Same concern for the IR guided missile.
The ground launched air defense missile is larger, which can have more discrimination capabilities due to larger computation power, so launching multiple missiles against a single target is more likely an operation. Even so, it is not without issues. Look at the single F-117 loss over Yugoslavia. That F-117 evaded at least two ground launched air defense missiles before damaged by the proximity explosion from the third.
I'm asking because there was this silly news in the Indian side of the media that an SU-30 'shot-down' 4-5 AMRAAM's;...
Bunk. That is all am going to say about it.