doing 3/4 without 1/2 is no problem
i'm not sure if the subject design has changed but if you've looked through the exams you'd realise that lots of questions really just repeat the answers' content. what i did for exams in 2013 was really just cramming all the exam answers in my head and memorising the works of two artists i chose. and from the exams and study guideline i printed out long lists of things like mediums and their processes, a list of preservation ways and a summary of each, a list of art terminology etc (probably like 5 pages of lists of things expanded from the content of the exams which still isn't much), so that's my advice, get massive expanded and detailed lists of info derived from the questions they ask. i just printed them off the internet and they're really easy to find anyway.
as i said, i don't know if the study design has changed or not. but with the two written components for sem 1 and 2 to write about your artworks, i'll talk about sem 1 because i'm more sure about it, i think it involved lots about writing about the PROCESSES of your artworks and WHY you've made the choices you had (like for added meaning, a metaphor??, to give dimension, to look better in WHAT way etc. also USE YOUR ART TERMINOLOGY). So unless you've used photography as a medium for your sem 1 it's not that necessary to know now, you can take your time until you actually use it and you'll know anyway, you won't be tested on it for sem 1 or 2 unless you've used it (then you'll know anyway) and will need to put it in your reflection for the artworks you made for the semester.
my major tip for you is to get a copy of the criteria sheet, your teacher may provide it to you or you can find it on the vcaa website somewhere. it's quite straight forward compared to something like the english criteria sheet, so if you nail down everything and make it detailed but still concise you'll get good marks.
my studio arts teacher was a past examiner and even she said that if you've studied about 20min for two weeks or something to memorise everything you're set. and it is no joke, there isn't that much content to learn in studio arts. but my teacher did give us fake sacs during the year that covers some of the content with made us familiarise with it though.
i'm sorry what i wrote aren't relevant if the study design changed!
have fun with his subject!!!