Second, you need to check out what your company organisation structure is in terms of authority (to make decision) and responsibility.
These should tell you whether or not you are allowed to grant leave without approval of your managers in the hierarchy above your. In case of doubt, send an email to your HR team and ask what you can and can not do.
HR policy is not a generic document that applies across companies. It is specific to your company. So you need to follow what your company has laid down