If you are not experiencing any DirectX errors, . Your current DirectX runtime (from Windows Update) is more secure and performant.
Many games require these alongside DirectX.
Version numbers can appear differently. Check the field or use a tool like System File Checker (sfc /scannow) . The actual build number 102902 may correspond to d3d9.dll 6.1.7600.16385 (which internally has a build tag 102902). Not all property sheets show the full internal build hash.
No. DirectX 11 and 12 use separate file versions. Installing version 102902 does not affect modern games.
Microsoft no longer hosts individual version 102902 DLLs, but their official redistributable contains exactly that version.