KVPY has three streams SA,SX,SB

Since you are in 12th...you belong to SX category

Here are the Eligibility details for SX paper

• Enrolled in 12 ^th Standard/ (+2) (Science subjects)
• They should be aspiring to join undergraduate program in Basic Sciences namely Physics/Chemistry/Mathematics & Biology leading to BSc/BS/BStat/BMath/Integrated MSc/Integrated MS for the session 2020–21.
• They must have secured a minimum of 75% (65% for SC/ST/PWD) marks in aggregate in Mathematics and Science subjects (Physics/Chemistry/Biology) in 10 ^th exams and a minimum of  60% (50% for SC/ST/PWD) marks in aggregate in Mathematics and Science subjects (Physics/Chemistry/Biology) in 12th exams.
• Students in their 2 ^nd year in Cambridge International Examination Board and aspiring to join a UG programme (viz. BSc/BS/BStat/BMath/Integrated MSc/Integrated MS) in Basic Sciences namely Physics, Chemistry, Mathematics and Biology.
  Such students must fulfil the below-mentioned criteria:
  a) Secured a minimum of 75% (65% for SC/ST/PWD) marks in aggregate in Mathematics and Science (Physics/Chemistry/Biology) in Class 11.
  b) Secured 60% (50% for SC/ST/PWD) marks in aggregate in Mathematics and Science (Physics/Chemistry/Biology) in Class 12 Board exams before taking up the fellowship, if awarded.

You can write the KVPY exam but your criteria does not fit into the eligibility criteria for KVPY .So dont waste your efforts by giving this exam

Hope this answer helps