GRE

You should check your ability to learn things, but it's nice when you start taking classes.
Joining a coaching institute will help a you a lot.

Of course! But you have to do IELTS or TOEFL which is compulsory and check for university requirements that it requires GRE or not. But its nice if you do it all along.

IELTS or TOEFL is compulsory. Check university's websites for GRE requirements, it may not be required depending on what you want to study and where.

No. GRE is not mandatory for admission in Australia. However you need to clear IELTS with 6.5 bands.

Majority of universities abroad use GRE scores for MS.

Hello,
GRE is not mainly required by European countries. I will advice you to look at the university website for particular information. Your query is very wide and does not specify anything.

You are eligible to appear for GRE even now as the only eligibility requirement for GRE is the document required to prove your identity.

GRE is not a must for PG Diploma programs, I will suggest you to look at the university requirements for the specific information you are looking for.

GRE is not required in most European universities. You can check a particular university for specific requirements. If your academics are not too good then you should take your GRE.

Master's degree from Canada depends entirely on the overall profile of the applicant, which includes following parameters:
1. Academic background and CGPA.
2. Research experience.
3. Projects undertaken.
4. Work experience or internship undertaken.
5. IELTS/ TOEFL scores (Average requirement for IELTS is 6.5 band and for TOEFL is 90).
6. Financial capacity.