hi,

from your statement, I come to know that you are having 4 years gap between 10th and 12th,  now see if you failed in 12th this year, you can apply for the compartment subject exam to clear the remaining subjects. in generally after the declaration of regular exam result , the date for compartment exam declares, if you can not clear this time in compartment exam, you need to apply as private candidate for 2021 exam,