M.Sc

Sure you can get a job.The 12th score will not much matter after you complete your MS.

You can try your hand at securing admission in N. L. Dalmia being the next best option for you in case somehow things don't work at KJ Somaiya. You can go ahead with applying for both MS and PGDM programmes and be rest assured that you will inland UPAT either of the best Institutes.
All the best.

Check out the below link:
https://www.shiksha.com/science/colleges/m-sc-chemistry-colleges-india
It will provide you with the list of universities for M.Sc Chemistry.

Hello Rahul,
It is difficult to answer since this depends on the university. There are so many in Australia. Your backlog is too much, I doubt if a top university like the University of Melbourne will happily accept. Keeping aside the backlogs, see that you meet the admission requirements, have the minimum academic percentage, required IELTS and so on. Apply accordingly. The entry requirements are naturally different from the universities so you have to visit the websites and start preparing accordingly.