Since you mentioned you are Sri Lankan I strongly recommend you avoid coming to India for flight training
The present system of pilot licensing in India is not kind to someone that does not hold an Indian Passport
You will face a lot of difficulty in obtaining everything from the computer number to the Indian RTR license
Not to mention security clearance for the Computer Number , For the RTR license ( you need a different security clearance for everything )
This security clearance is not time bound and can take months if not years to come by
If your Grade 10 and Grade 12 was not from an Indian school you will need to go to the Association of Indian Universities in New Delhi to get a document saying its equivalent to the Indian system ( assuming they do approve , if not then you the dgca wont issue you an Indian pilot license )
Lastly after obtaining the Indian license you will need to go back to Sri Lanka and convert . I dont know the procedure for conversion but I strongly suggest you look into that first . It can be very difficult to get the DGCA to send the verification letter of your license to the Sri Lankan authorities
Why dont you look into flying schools in Sri Lanka or US / UK / Canada etc ?