Some programs restrict your choice as to what electives you can pick (eg, comp eng) - they might restrict you to a list of COMP subjects. A 'free elective', on the other hand, allows you to pick any elective you like. You usually only have 'free electives', if you have restricted electives (otherwise you wouldn't be calling them free electives).
Gen eds are courses usually taken outside of your field of study. For example, if you are doing a science degree, you are not allowed to have more than 3uoc of gen eds from the science faulty, or have more than 6uoc (accumulated) from any other faculty. The idea of gen eds is to expand the knowledge of UNSW students. These courses are generally easy subjects.
Maybe someone in a combined can help with the second question.