Hi Shubham, no you don't need to sit for both the exams, you can go for either of the two. My brother had a similar query so he got in touch with experts at Leverage Edu who helped him understand everything about the exam as well as about the universities that accept IELTS and TOEFL. In fact, they also helped him with the preparation of the exam. You can get more information on this link (https://leverageedu.com/blog/IELTS/) .

No, you can answer either of them. Both IELTS and TOEFL are similar examinations and come at similar cost. In UK, however, its IELTS, which is more prevalent and accepted by more number of Universities, while in US, TOEFL is accepted by more number of Universities.