Though your results have been announced in January, because the Academic year closed in 2018, you will be considered 2018 passed Candidate. And so you will be eligible for BITSAT 2019 and not BITSAT 2020. According to the official website: https://www.bitsadmission.com/bitsat/2020/BITSAT-2020Brochure.pdf , it says that Candidates who have passed their 12th either in 2018 or before are not eligible for BITSAT 2020. You were eligible for BITSAT 2019. For BITSAT 2020, Candidates who will complete their 12th in 2020 or who have completed their 12th in 2019 are alone eligible. But because you have completed your 12th in 2018, unfortunately you are not eligible for BITSAT 2020.