The competition notice or call for expression of interest describes the minimum requirements in terms of qualifications and professional experience. It also describes the nature of the duties you may be required to perform.
Anyone who meets at least these minimum requirements and whose qualifications/experience are relevant to the duties in question may apply.
Even if you have additional qualifications and professional experience, you can only be recruited at the grade/function group and for the profile specified.
For example, if you have a bachelor's degree you may still apply for an assistants' selection procedure, where only a post-secondary qualification is required. You should carefully read the nature of duties, however, to ensure that you have the right experience and motivation to perform the duties required.