BDS

Chances are there but most dental programs and universities require prior practical experience to be eligible. International students must also take IELTS, required score is IELTS 6.5 with at least 5.5 in each component. You should visit university websites for specific details.

Agriculture and BDS both have very well scope and have equal importance. You can select anyone of the courses based on your interest in future aspiration. However, I prefer that you apply for BDS course instead of agriculture as it has better scope.

Yes, but difficult for international students if you are not strong academically. You must visit university websites for program details and entry requirements meant for international students. Every university has its own entry requirement. You may opt for Masters in Dentistry, Dental Surgery, Dental Public Health, PG Diploma in Dentistry etc. Check Cork University Dental School and Hospital, Trinity College Dublin and the very famous Royal College of Surgeons in Ireland (RCC).

Hi,
For BDS or MBBS programme you have to face the entrance test, especially in BHU.
You need to fill the application form and follow the admission process accordingly.

If you want to do internship and practice in India, then you have to qualify an exam conducted by MCI to check your eligibility and provide permission for the practice.
Good luck.

Hi,
Certificate courses after BDS:-
Post-Graduate Certificate in Oral Implantlogy (PGCOI) - IGNOU

You can pursue Master of dental surgery. There are many specializations available like oral and maxillofacial surgery, oral pathology and microbiology, pedodontics and preventive dentistry, etc. You can choose your specialization as per your interest.
You can also opt for PG Diploma programs in these areas, but if you want to practice, MS is recommended. You can also check certificate courses in cosmetic dermatology, endodontics or cosmetology and Diploma in dental assistance.

You should aim to secure at least 460 marks for a good private dental college, but cutoff varies along with different states.

With 25000 rank from general category, you may not get any government MBBS or BDS seat. You may get private colleges with this rank.
All the best.