Welcome to the community some information which i could gather is as follows
For major conferences in India visit http://www.conferencealerts.com/country-listing?country=India
For contests for students.
Annually Intel Education initiative organizes an annual Contest for Teachers of all disciplines, where students digital work becomes part of the portfolio which is gauged by neutral judges, and fabulous prizes are awarded besides an Annual Science fair, is also held annualy final nominees travel to USA and participate in the Annual International Science and Engineering fair (ISEF).
please get in touch with the local Regional training agency in your area. The Deadlines will also be communicated
Also Google and other international orgs. have started doing the same, as for Google,students can register through the Google Science Fair website, although they will also need the consent of a guardian
(parents or guardians).
jetted to Google HQ in Mountain View
Best of luck for now.