Yes, the reconcile process must be applied on all versions to reflect changes in a dataset. This process is done to ensure all versions of the dataset are identical in the geodatabase.
Reconcile and post processes typically take place in tandem if specified in the reconcile tool.
When a project or work is started in ArcMap, a version can be created as a child of the DEFAULT version. The child version can be edited by one or more editors. Once editing is complete, the editor or ArcSDE administrator reconciles with the DEFAULT version, resolving any conflicts. The modifications are posted to the DEFAULT version, integrating the edits of the version to the published database.
Users must reconcile and post versions in order, starting with versions farthest removed from the DEFAULT version and moving backward.
The version to be reconciled must fulfill certain pre-requisites. For more information, refer to the following documentation, ArcGIS Help: A quick tour of reconciling a version.