Will i be able to get delhi domicile benefit in neet 2020 if i did my 12th from delhi in 2018-19 and take an year gap

You cannot claim Domicile benefits of Delhinor for that matter any State because you have pursued your 12th there. According to he rules of the Government of Delhi, to claim domicile certificate of Delhi, you should have atleast stayed in Delhi for the past 3 years. Because you are a minor, any of your parent' s name should be in the Voter's list and of that is the case, domicile certificate will be issued based on your parent's residence.