courses to become a Doctor

Hi,
They have pre-professional studies in medicine for which you must have completed your university degree, you can apply for your Bachelors there itself, please contact them for details:
https://www.brandonu.ca/future-students/programs/pre-professional-programs/
Here are some health studies they offer:
https://www.brandonu.ca/future-students/programs/degrees/

Yes, you are eligible to study the respective course, if you have achieved a good rank based on your caste specifications. You can make use of Shiksha rank predictor, to predict your approximate rank.

You can go for veterinary doctor. Also, there are other courses like BAMS, BHMS, etc., but the entrance test for these is same as of MBBS i.e. NEET.

Please refer to the link provided below for a list of top colleges for M.Sc. courses in Assistant Physician Course. You should be able to navigate to a college of your choice.
https://www.shiksha.com/medicine-health-sciences/paramedical/colleges/colleges-india

Hello dear,
You can add a doctor predix by various means. You can pursue MBBS, BDS, BAMS, BHMS, BVSC, BUMS, etc. All of these courses will entitle you a doctor prefix.

Hi,
You cannot study medical without a relevant background, since you had commerce I doubt if you are eligible. You can check for associate degree programs which are of two years before proceeding to a Bachelor's degree. I would advise you to check directly with the colleges.