GRE

Hi Aditi, you may do so. The sooner you prepare the better it is. It will also save you from additional gap years in future which you might require for your test preparation. However be aware about validity. GRE scores are valid for five years while TOEFL scores are valid for 2 years.

Hi Viraj,
You can do MBA after gaining some work experience and after taking GMAT and TOEFL. Since your academics are not great you must build a good overall profile. MBS admissions are one of the most competitive.

Do you want one book for all exams? Each of these exams are unique and need different preparation for IELTS prefer Cambridge prescribed book or visit Brirish Council Library. For CAT RS Agarwal, Nishit Sinha Sarvesh Varma, Gautam Puri are few recommended books also try tcyonline and other portal. Manhattan, Kaplan, Argo are few of the recommendation for GRE for other competitive there is a lot of definition of other and there are 100+ competitive exam. Be specific with what you want in life and keep.

USA has best education facilities in the field of computer science. It is worth doing MS in top universities. Education in USA for International students is very expensive. With visa restrictions chances of getting a job for Indian students is full of challenges. If you do not have any financial problem or issue, you may go ahead with MS in USA universities otherwise you may look for some other options such as MS in German universities.
GRE requirement of International universities vary in different universities.

Your medium of instruction will not be a barrier. So many people from different cultures go abroad to study. If you are planning for UK take IELTS. Get your basics right, practice a lot. GRE may not be required. Exact inf will be given by the university.

Hi Gobind, if you want to study in Canada then GRE is not even required so there is no need to stress on it. If the university you are planning to apply to requires GRE then your question's answer will be found on that particular university website but generally GRE is not a requirement except for technical programs in Canada.

From which college did you complete your PG?

There are universities like Thompson Rivers and Vancouver Island University which do not require GMAT. You may check their websites for details.