Hello

You so not need a domicile certificate to get admission via All India Quota. You can get a reservation of 27% under OBC category (however the cutoffs for general vs obc category is not much). If you want to get the benefits of reservation in your domicile state (maharashtra) then you will have to get a caste certificate made in that state

I will advise you to get a fresh obc certificate issued by central for the current financial yesr for you to be eligible for the obc category reservation in NEET 2021. For more information you cn click on http://www.ncbc.nic.in/User_Panel/UserView.aspx?TypeID=1176#:~:text=National%20Commission%20for%20Backward%20Classes