Sales & Marketing

Yes a bit because canada has wider market than australia. moreover working population in canada is lesser than australia. saying this I do not mean that australia is complete no. in case you have relatives in australia, they may recommend and it may work in australia too, just that a lil difficult.

Hello, well it depends where you want to study. Not all universities require GMAT or GRE. As an international student however you must take TOEFL or IELTS.
Regards

It is true that finance and marketing specializations have a ton of offers, but it does not mean than other departments are doing bad. Choose what you love doing and don't worry about placements, eventually you'll end up well.

Both specialization have its own advantage. It depends on student and his interest. Being a commerce graduate,if you are creative and keep good analytical skills, then marketing as a specialization is good option. As you are introvert but have analytical skills,then finance as a specialization can be another option. Finance is not tough for commerce student.

You can find out thousands of opportunities in Marketing and Sales. But many companies looking for Graduates only. Do not disappointed, but its a fact. A graduation in any stream is the minimum requirement to start a career in sales/ marketing. The promotion will be based on performance.We can see that Many Marketing VPs who does not have MBA / PG. But MBA is an added advantage.
Try to pursue Graduation. But do not think that only graduates can enter into marketing. There are opportunities for HSc and Diploma holders too.Skills are more important
All the Best

There is no such package number that one can arrive at. It clearly depends on the capabilities of the candidate.

Yes definitely because they have work experience they know how corporate works.

Every course has it's own importance.
Select the course of your interest.

No, they have a BBA (Accountancy) program. for details and programs offered please visit the website. Here is the link
http://www.nus.edu.sg/oam/programmes.html

Yes, it has good scope and attractive pay scale. Admission requirements are different. Which country or university have you planned to go to? Generally you must clear GRE or GMAT and TOEFL or IELTS. But requirements are different as mentioned.