Yes, you can navigate through questions by choosing the NEXT or BACK buttons.
The ASPEQ system also has a question number 'progress indicator' at the bottom of the screen which is colour coded to show whether the question has been answered or pending, etc. and you can go back to specific questions via this 'indicator'.
There is also provision for leaving typed comments against questions, which can be done at any time during the exam but for which an extra 5 minute period is added at the end of the exam.
2104 is a tad ambitious, is it not?