ACT

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.

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.

SAT and ACT are standardised tests which students need to take if they are planning to study in the US. Not all universities require SAT/ACT. You can take the SAT or ACT by creating an account on the respective website Collegeboard.org for SAT and ACT.org for ACT.

Both of these are the entrance tests for doing engineering related courses abroad. Please upvote if you found this answer useful.

Hi Swapnil,
I believe you are enquiring about scholarships. If yes, then please know that there is a difference between fellowship and scholarship. Be careful with the terminologies when you are applying abroad. Scholarships are on merit-basis, a high SAT or ACT score will increase your chances, however, not a guarantee. You must be a brilliant student overall.