Epic will add the DX12 stable version probably this year or next idk why you need DX9 (DX10/DX11/DX12) if you don’t have support for DX10 you got a real problem with a older computer than 8 years and Windows XP is not more supported.
*Metro Redux versions don’t work DX9 from what I know and S.T.A.L.K.E.R.: Call of Pripyat is from 2010. Welcome to the future we are in 2016 and the games will use DX12.