TOEFL

IELTS acceps all over the world, even US midst of the institutions accepting IELTS.
TOEFL is an online exam. IELTS you have to write manually.

ToEFL and IELTS ARE VALID ONLY FOR TWO YEARS. Hence you do it before you plan to go abroad

IELTS and TOEFL are language proficiency exams and GRE is competitive exam for Masters in US or Germany.

Yes why not if you can.

Dear Zeeshan, the actual conversion for the CGPA lies with the university & none would have the exact idea. Still you may self check it on the website for WES credential evaluation @ http://www.wes.org/students/igpacalc.asp.

Dear Steffi, 2 years is a pretty long time to study GRE & TOEFL as generally the students take 3 to 6 months to prepare & give the tests.
Since you are doing B.Sc which reflects your interest to pursue your Ms in USA BUT, to remind you that US universities would need a 16 years of education background or a US comparable degree to give you admission for their Ms courses.

To do your masters you will not have much schorlarships. few you can apply and try. PHd normally is fully stiphened PROGRAME. First you have to apply with good research proposal get ypur admission and then apply for schorlarships

IELTS is preferred over TOEFL.in Europe. But, you cannot apply directly after 12th since German universities require 13 years formal education. You can clear IIT JEE advance or complete the first year of a bachelor's degree program here in India as a pre requisite. Visit daad website for more details.
Thanks