Even if you are appearing for 12th, in 2020, you can still appear for NEET. Your admission will be provisional based on your eligibility in 12th. And your qualifying code will be 01. Code 01 says: A candidate who is appearing in the qualifying examination, i.e., 12th Standard in 2020, whose result is awaited, may apply and appear in the test but he/she shall not be eligible for admission to the Undergraduate Medical Courses, if he/she does not pass the qualifying examination with the required pass percentage at the time of first round of Counselling.