GRE

It all depends on your test scores and the scores that you've got in your last college/university attended. All this will decide if you will be selected or not. Check on the website and apply.

Your CGPA and GRE score are both not amazing. You can get admission in the top Colleges only if all other components of your college application - like essays, recommendation letters, SoP, extra curricular etc. , are superb. If not, then you should plan and spend some time on building your profile before applying to the top colleges in US/Canada.

Hello,
Your marks are too low and it creates problems for your higher studies abroad. First thing that you can do is repeat your class 12th if possible and if you dream is to study abroad then I suggest you to first complete your UG from India and after this, you can pursue PG abroad.
All the best.

Hi Vedant,
GATE scores are accepted in Germany. However, you should check the entry requirements, you may not even require to take any test other than IELTS and German language proficiency tests.

You should take GRE and IELTS at least two months before the deadline.

Hi,
Some popular ones are mentioned below:
For GRE follow ETS: GRE The Official Guide to the Revised General Test, Kaplan's GRE Premier and Barron's GRE. A number of practice tests are available online. For TOEFL : Official Guide To The TOEFL by ETS, Cambridge Preparation for the TOEFL Test etc. For IELTS The Official Cambridge Guide to IELTS Official IELTS Practice Materials (1 and 2) by British Council
Cambridge ESOL
IDP: IELTS Australia and so on.

Yes, you can prepare for CAT and GMAT together, because mostly, they would be the same. GMAT is for seeking MBA and GRE is for M.S. opportunities.

Some colleges ask for its scorecard, so you may consider giving both the exams.