Well, right now it is suggested that you should focus completely on your 12th board. After this, you first research a bit about IPM and how much time it will take to prepare. With such data, you can start preparing for IPM and by the time your exam comes, you will be ready.
As much as I know about IPM, it consists of 60% of quantitative aptitude and 55% of which includes higher mathematics, which is basically your complete 11th and 12th mathematics.
IPM Aptitude Test Pattern:
As in the interview, the questions which are asked basically depend upon the subjects you studied in 10+2 and your career aspirations. Be well aware of the current events and trends. If you follow these points, your exam would become a lot easier.