IIT

The government has decided to waive the full annual fees for students from SC/ST, differently-abled and economically weaker sections from 2017.
Students from families with an annual income of less than Rs.1 lakh will be able to study in the IITs for free. But, those belonging to families with annual income of less than Rs.5 lakhs will be entitled to a waiver of two-thirds of the fee irrespective of their category.

Yes, you can get admission. Diploma and open learning, both are valid.

There is no set of rules. Every student is different and has their own style of studying, so you can surely look at some generalized tips over the web to study, but eventually you will have to figure out your own way and schedule for studying.

You are advised to appear for GATE and score very high to get admission in M.Tech CSE at IIT.

Admission in IIT and NITs for MBA is done on the basis of CAT score.

IISc and NITs are good options for doing M.Tech beside IITs. If you are CSE or IT graduate then IIIT are equally good options for doing M.Tech.

In top IITs, the highest package offered is Rs.50 LPA, depending on your capability.

IITians with an innovative idea and solution which meets a company's competitive advantage needs can get best of International/ national salaries. For example, IITians who have their own original ideas on search engine are able to get job in Google with International salaries in the range of even one crore or more per annum.

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.