As far as mathematical skills are concerned, try to focus more on clearing your basics. Ratofy the formulae byheart them, and solve as many as practice problems as you can. Data analysis and sufficiency is the most scoring section and you've to score well in it and that's only possible when you solve previous years question paper of this section. Verbal and non verbal types of questions are asked in the Intelligence and Critical Reasoning Section. Fetching marks in this section will give you a great boost in your rank and may fix up your seat in your dream college too. Questions in Indian and Global Environment section cover the topics related to GK and current affairs. This section can be much scoring, to prepare well this section, you must read magazines & newspapers, watch news channels and be updated with the world. And the remaining section ie Language comprehension, Reading questions before reading comprehension makes it easy to find the answers well. Grammar plays an important role, so be sure to have a good command over it. Read English newspapers, watch English news channels, improve vocabulary and reading skills.

Now coming to your question part, you can take help of apps like GradeUp, U academy Learning app, ExtraMarks the learning app, etc.

Best wishes. Thank you.