My question is that sat and TOEFL is necessary for study in USA but any other exams will be taken by university for b tech degree.

No, a TOEFL-iBT score of 50 is likely too low for getting a seat at Carolina Uni. As per the university's admission policy, international students usually need an overall score of atleast 60, a paper-based score of 500, or a computer based score of 170 to study here.

Most UK universities accept IELTS, TOEFL iBT, and PTE Academic. Here are the standard benchmarks for Master's programmes:

IELTS: Overall 6.0 – 7.0 (with no individual band below 5.5 or 6.0 depending on the university).

TOEFL iBT: 79–100 (varies by university).

PTE Academic: 50–65 overall (roughly equiv

One good book is enough for most students. But many buy 2–3 books, one for official practice and others for extra questions. Avoid buying too many. Focus on quality practice and reviewing mistakes instead of collecting many books.

The Official Guide to the TOEFL Test by ETS is the best. Barron's TOEFL iBT and Cambridge Preparation for the TOEFL are also highly recommended. For Speaking and Writing, use books with model answers and audio. Pick according to your weak sections.

Choose books that match the latest TOEFL pattern. A the latest publications should be priortised. The best ones have full practice tests clear explanations, and answer keys. Always check reviews on Amazon or Reddit before buying. Official ETS books are the safest choice.