Hi there,

Some of olympiad for class 12th students are following:

National level science talent search exam.

Kishore Vaigyanik Protsahan yojana.( for science students)

IOEL ( International Olympiad of English language)

INO ( Indian national olympiad)

National science olympiad

For more details follow this link: https://www.google.com/amp/s/school.careers360.com/articles/scholarships-in-india/amp

Hope it helps you

Good luck!