TOEFL

If you apply in USA universities, then you have to appear for GRE with TOEFL. For other countries, you don't need to appear for GRE, only TOEFL or IELTS is enough. But if, your academic record is not up to the mark, your GRE marks help you to get admission there.
For MBA admission you need to appear for GMAT with TOEFL or IELTS as GMAT is must for MBA in abroad.
All the best.

TOEFL (Test of English as a Foreign Language) and IELTS (International English Language Testing System) are two of the most widely-accepted tests to certify your English proficiency. The decision on which one to take among TOEFL & IELTS depends on a number of factors.

Hi Dilpreet,
You must understand the differences between the two, opt whichever you think is easier for you. Different test takers will have different opinion hence go by your comfort level. A number of blogs are also available, you may check them on the internet. Here is one for example:
http://ieltsadvantage.com/2015/06/17/ielts-vs-toefl-which-is-easier/

Yes, you can appear for these exams again.

Yes, you need to have a passport if you are appearing for GMAT, TOEFL or IELTS exam.

CATIA is a job oriented course. It will be a good idea if you complete CATIA, do a job and then pursue your MS or even MBA. If you get an year back, doing CATIA will help in improving your profile.

No, TOEFL is totally different.

Both are very much mandatory.

Unfortunately, not possible to study in Stanford University without appearing in SAT and TOEFL.

It needs around 4 months maximum but it depends on your ability and hard work. So try as soon as you can. Try 1 full mock in every 2 days as there are various TOEFL software available in internet. You can download them and start practicing. You can also get help from google play.