SAT

The Scholastic Aptitude Test (SAT) is a standardized test widely used for college admissions in the USA. It was introduced in 1926. The SAT is owned, developed, and published by the College Board, a private, Not-for-Profit Corporation in the United States. It is administered on behalf of the College Board by the Educational Testing Service. It is designed to measure important skills required for academic success at undergraduate degree level and the current version contains three main sections measuring basic critical reading, math, and writing skills, as well as open category not included in the final score. The SAT is typically taken by high school students who require entry to colleges and universities in the United States; other countries (e.g., Israel, Sweden) have also adopted the SAT as entrance exam for admission to higher education institutions. The SAT contains 3 hour and 45 minutes of actual timed sections.

Hi, universities will open the admission rounds after August so you have to keep checking, deadlines differ from university to university, since you will be completing your exams in March 2018 you will have ample time to prepare and apply for the Fall 2019 intake. 6 to 10 months is generally required to prepare for the admission rounds. Start preparing early so that you can apply early. Ivy Leagues are not just about passing your exams with high grades but you must be an all-rounder to fit in. Take part in extracurriculars, do voluntary works, projects etc. See on what ways you can compete with other applicants. You can take the SAT this year so that you can focus on your boards. Or immediately after your boards.

Hi Nilay, what you should study should be known to you, if you still haven't decided then I think you are not prepared to go abroad yet. If you are confused with the subjects then find out your aptitude, likes and dislikes, favourite subjects, most hated subjects etc. There are many courses offered by universities in US, you can browse through university websites and find relevant majors etc and also you can choose your major later.
To get a scholarship you have to do well in your academics, SAT etc and must also have extracurricular activities. Target a SAT score of 1400 and above. Start researching on university admission requirements and prepare accordingly.