BBA

No, you cannot have such chances. You need to go directly from the first year and then you can complete BBA which is recommended and apt for you.

You're required to have minimum 12 years of primary and secondary education and should have Senior Secondary Certificate of Education or an equivalent certificate from India.
You should apply to your desired universities. The university courses in Australia usually begin from early March so make sur

MITSOB is better college for BBA.
You can check the below mentioned link:
https://www.shiksha.com/bba/colleges/bba-bms-bbm-bbs-colleges-in-pune

Symbiosis in the best option.
Good luck.

BBA will give you a wider scope in all the aspects of management, whereas, BAF would be more focused on the accounting and finance aspect of the business.
It depends on your interest.

That depends on the board of education and institute you're studying in. In the commerce stream, you have to use the fundamentals of maths.

After completing BBA, you should opt for PGDM. It is the best option for you.

BBA is relatively an easier degree in comparison to B.Com. As a science, student it will be too theoretical but quite easy for you.