Patches are cumulative; each successive patch includes all of the fixes from any previous patches. As a result, a newer patch can be installed on top of an older patch. The patch number, which increments itself for each successive patch, indicates the version. A patch with higher version number can be installed over a patch with a lower version number.
The Installation software checks the version of the installed product and the version to be installed at the beginning of its process. It will not allow an older version to be installed on top of a newer version.