Whicb course pursuing after 12th to start my own model company?

If you wish to go into the field of forensic Science after your 12th, make sure you focus on PCM/PCB subjects and score well as many colleges take admissions based on that merit or appear for the accepted entrance exam. You can aim for a reputed college to pursue a BSc in Forensic Science followed b

It's difficult but in some colleges you may can get 

Yes, you can pursue VFX after completing your 12th grade. You need to choose the right subjects to develop foundation as a VFX artist.

A gap of 1 to 2 years after 12th can be considered normal. Although the students should be able to address it via the valid documents. The reasons like health, finance, skill development or family are accepted. 

And if the gap after the high school Diploma is beyond 2 years, strong documentation

Yes, it should not be hard for you to get admission to the University of Western Australia as an Indian student with 50% in class 12th. However, please note that it does not put you in the top applicants either. The general admission percentage requirement for international students is 50 to 65%.

Loo