TOEFL

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.

Your CGPA is enough to get admission in the best universities in Canada, so GRE is not required, but you can go for either TOEFL or IELTS, Canadian universities accept both the exams.
All the best.

Hello Simon,
For procedure to apply for these exams, please go on the below link:
For TOEFL
http://www.toeflgoanywhere.org/
For IELTS
https://www.ielts.org/
From here, you will get all information.
Yes, you can apply it for anytime.