IIM

In the last of your interview, the interviewers should be impressed by you. Impressing the interviewers mean, they are convinced of your expertise, experience, desire, motivation, devotedness, entrepreneurship skill, managerial skill. Maybe anyone of these or each of these. Many a time, anyone of these is enough to get you in.
Now, the interviewers sitting in front of you can be fascinated in various ways which will depend on you.
Some would say communication skill is the necessary component. Some would say knowledge of current affairs and your subject matters. Others would say, your enthusiasm and being you is the key. There are many other views likewise. People discovered different ways to convert IIM calls. They may work for you, may not. You have to find your own way. There is no written rule that can lead you to the place where you want to be.

Yes, you can surely apply for an IIM even you have rejected a previous offer. There are people who do get selected in newer IIMs but they apply again to get into top IIMs. The shortlists are based on CAT score and profile and the number of attempts are not considered. Normally, during the interview process as well, the interviewers do not ask about whether you were selected last time. If they do, then you can give a valid reason for your choice and make them understand the opportunity cost of your decision. If you wanted to have work experience before joining IIM, then you can justify your choice. Having said that, you should really think beforehand whether you want to join or not. There is no guarantee that you will get a call this time if you get it before as it's all relative to the quality of candidates and CAT score.

Written Ability test is conducted by various IIMs to check your awareness, analytical and reasoning, the structure of thinking and writing skills. The topics can vary from current affairs, abstract to general opinion on a topic. It's important to read editorials from newspapers like The Hindu which gives an idea of how to write on a particular topic. You can also check the website (http://www.insightsonindia.com/) and watch RSTV debates which are used by candidates preparing for IAS. It needs the practice to follow the structure (introduction, body and conclusion), make logical arguments, avoid grammatical mistakes and write the article within the word limit. Also, it is expected in What that you take a side on a topic and justify it. Although, it depends on the topic. Even if the topic is abstract.

Let's start with the rankings. IIM-Ahmadabad stands at 1st position. IIM-Bangalore stands at the second position. While IIM0Calcutta stands at the third position. So, the top three positions are occupied by the prestigious IIMs.
Following them is XLRI-Xavier School of Management and IIM-Lucknow.
Now, comes the turn of our college in focus-Faculty of Management Studies, University of Delhi.
So, it is ranked 6th according to the rankings given here which took in account rankings from various sources.
For entire list check:
https://www.shiksha.com/mba/ranking/top-mba-colleges-in-india/2-2-0-0-0
So, FMS is pretty good. So, if you aren't getting any of the top three IIMs, you can consider this college. The infrastructure and facilities are pretty good. The average package is around 20 LPA which is at par with the IIMs.
So, it is a pretty good college.

Well, CV doesn't have points, it always carries weight. How strong your CV is and how capable you are. The most important thing which will be considered during your placements is your CGPA. Companies will shortlist mostly on the basis of CGPA. There have been times when the list of shortlisted candidates for some of the best firms consisted top 10-20 rank holders of the college (literally). So, no matter what anyone says, CGPA shouldn't be neglected. Especially for high demand jobs like investment banking, CGPA is a deciding factor.
After CGPA, they will check for relevant internships. So, make sure that you do at least one or two internships in relevant fields in good companies so that you don't look like a novice. Then they see the past academic records and awards and honours including scholarships and fellowships.
So, the order of importance would be:
1. CGPA
2. Relevant internships in reputed companies
3. Awards and Honors
Don't think that extra-curricular activities matter a lot. It is good to have some to show that you are an interesting person. It may have a bit importance in marketing but not at all in finance. Having important position of responsibilities like the president of the student council or something may be helpful.
But don't neglect academics for that.

The IIM tag promises the average Indian kid a better life. There is enough proof in the newspapers with reports of the sky-high salaries during the annual placement seasons at these top-level institutes.
I believe that almost anything can be learned off the internet. But the benefit of an education in an IIM is the exposure that they provide. Those from institutes other than the IIMs also make it big and have humongous salary packages. To get into IIMs one has to crack the prestigious CAT. CAT is the exam for smart people, so if you are from IIM, it means you have cracked it. That leaves an effect on the minds unknowingly. People are biased about IIM. So it affects the CV of the students. Having a degree from a top business school increases your chance of landing that job. It is not very much prominent but it is a factor.

Until a decade before, IIMs were the most desired B-schools. In 2009, things started to change with the opening of several new IIMs, starting with IIM-Rohtak, and followed by more, in Ranchi, Raipur, Trichy, Kashipur, Udaipur, Nagpur and six other cities. While this means that the aspirants have an elevated chance of getting admission, the value of brand IIM has been eroded in the method. The new IIMs have not been able to match the standards of the older ones on various parameters, including the quality of faculty/students, infrastructure, as well as ability to attract top recruiters.
Apart from quality education and research work of students and faculty, the older IIMs had been valued chiefly for the high-paying jobs their students got. This led to high expectations from the newer IIMs too. The reality has turned out to be contrary.
The newest IIM Jammu, IIM Bodh Gaya and a few others still have to get a campus. Though faculty shortage is affecting nearly every B-school, the situation is worse in the new IIMs, partly due to their geographical location.
So I think the government should focus on developing the older ones instead of opening new IIMs.

IIMs and IITs are really focused colleges and can't be compared to the US and European universities. Those universities house various departments which all come together to enrich the student experience. And, additionally due to the smaller size of the universities in India, they have low number of foreign students and faculty. Also, the research output is lesser than universities worldwide due to the focus on placements. But, in general the kind of students that enter and the faculty that teach are the smartest and most hardworking in the world. Also, both the institutions have good penetration in the network, and the students and research benefits from it.
The ranks are for the one year MBA program of IIMs, and don't represent the quality of their flagship PGP Course. Hence, I would say these rankings are not a good metric of assessing/comparing the quality of IIMs against other institutions.