Hi Kesavan,
For API functions, have a look at the "core_course" area on this list: https://docs.moodle.org/dev/Web_service_API_functions.
For information about authenticating and calling Moodle's web service API, see https://docs.moodle.org/dev/Creating_a_web_service_client
For further info, see https://moodledev.io/docs/5.0/apis/subsystems/external
However, if you are really using Moodle 3.2 you will notice that a lot of those functions were added later. 3.2 has been end-of-life for over 7 years so you will find it difficult to find people who can give you relevant advice, not to mention that there will be serious security fixes you are missing. I would highly recommend you upgrade to a supported release before attempting custom development.