SAT

Hi Likhith,
Yes, you can take the SAT and re-attempt it if you are not happy with the scores, so taking the SAT in 11th is actually a good idea.

Hi,
Three to five months is a good time. Dedicate at least 5 to 7 hours a week to complete your schedule on time. That said, every individual has his own routine and caliber. You have to know yours and plan out accordingly.

Hi,
Yes, in that case you can start your classes from 2020, the admission process starts one year ahead. If you are okay with the gap you may go ahead.

TOEFL- If you are proficient in English, then you should not spend more than a total of 15 hrs. Just solve few sample tests. Same goes for IELTS. If you are moderately proficient, spend 2 hours every day for 3 weeks.
For SAT and ACT: It depends on your proficiency and your target score. If you are aiming for the top 10 percentile and also are quite proficient already, then spend 3 hours for 2 weeks solving papers and revision. If you have just started preparing, then spend 2 hours for 3 months to gain good understanding of the test pattern and to do well.

Hi Anushka,
If you want to study abroad then you need to specify or mention which country you want to study in. In USA SAT or ACT is compulsory while it may not be required for many other countries.

The SAT Subject Test in Mathematics from class 11th (formerly known as Math I or MathIC (the "C" representing the use of a calculator) is the name of a one-hour multiple choice test given on algebra, geometry, basic trigonometry, algebraic functions, elementary statistics and basic foundations of calculus by The College Board.

4-5 times in a year with a gap of 21 days.

Most of the scores are valid up to 2 years from the date you took the exam. Every country has different criteria and different requirements of the score for admission.