You can access to every place inside the Alhambra (Alcazaba, Nasrid Palaces, Partal and Generalife) just once. However, you can go in and out of the complex all the times you need.
For example, if you want to visit any of the areas in the morning, going out to have lunch and coming back to continue, there is not any inconvenience, always taking into account the opening hours of the monument and the special time for Nasrid Palaces.