Civil Servant (IAS/PCS)

Maximum of the best coaching institutes are in Delhi. There, Vajiram and Ravi are the best according to me because they are the oldest institutes and give coaching for Mains, Prelims and Interview as well.

Its great. You can definitely become an IAS officer. But keep reading newspaper daily and also concentrate on current affairs. Also, make it a habit of preparing your own notes.

There is no minimum percentage requirement. You should only have a degree certificate from a recognized institute.That's it. Generally the UPSC board doesn't give preference to academics. Its purely based on marks scored in UPSC exam.

Yes, after cracking UPSC prelims and mains with good marks, you are eligible for personnel interview. As per my knowledge, if you crack the interview, you will be an IAS officer. You have to study very hard for that. Your world should be limited up to you and your studies.
Best of luck.

MBA in marketing is known to have better opportunities, and IAS is an excellent option which requires a lot of hard work. I would suggest you to look at the type of jobs you might enjoy doing and the type of subjects you would like to study and then make a decision rather than make a decision purely on package basis. Because, if you choose marketing and if you are not good, they were will be a lot of people who is better than you and hence you might not be able to perform much. Play to your strengths!

A search on the net will lead you to many coaching institutes for IAS preparation. Getting a comparative study is also easy now-a-days. I want to tell you about some latest options for coaching. Many people are opting for online coaching classes which are affordable and good. They are conducted by experts so you need not worry about their effectiveness.
For example a visit to a site WizIQ.com will show that there are fifteen different types of courses (https://www.wiziq.com/courses/search.aspx?qry=IAS) available. You will get an idea about their popularity from the number of students taking the course. No harm in exploring.

After completing your class 12th from any stream, you can do your graduation. A civil service exam is conducted for which graduation is the minimum requirement. You can join a coaching to prepare for this exam.

To become an IAS officer, you need to qualify the civil services exam. For which you need to complete your graduation. IIT is an engineering institute, and to get admission in it, you need to appear for an entrance exam just after you complete class 12th (I don't know the aggregate). Both of them have a great scope. You can opt for any of them. You can appear for civil services exam after completing your B.Tech from IIT.