TOEFL

Without these tests, you will not get admission in a good University. These tests are necessary to understand your reasoning and English language skills.

Yes, these exams are for higher studies in foreign countries like MS, MBA, etc.

Both exams are equal. The difference is TOEFL is an online exam, and if you are familiar with key board typing you will find it easy. IELTS you have to write the exam manually by hand. Both the exams have same standard and you cannot tell one is easy.

You should use Shiksha's abroad study counsellor service. They will also be able to calculate your chances of admission in a university.

National university of Singapore and Nanyag Tech Universities are the top most universities of Singapore.
All the best for your bright future.

GRE is an examination conducted for admissions into various colleges and universities in US. It primarily tests your reasoning ability. GRE score is considered by top colleges. TOEFL is an examination conducted primarily to test your English. TOEFL score is compulsory for education abroad. If not TOEFL, IELTS will be compulsory.

Yes, most of the universities in London accept TOEFL score.

Yes, you can. The scores have a validity of more than 1 year. So, you should be able to do so.

No, without this also you can do MBA. If you apply for freshers MBA in the UK, there no need of GMAT or GRE. If in your class 10th and 12th exams, you scored more than 70% in English, you can get an exemption for IELTS or TOEFL.

Do you want to study abroad or work abroad after studying in India? For the latter part, I would suggest complete your PG by either M.Des or MBA. Both have a good demand in foreign nations. Also give IELTS or TOEFL exam and check colleges that will give you admission based on your score for studying abroad.