From what I have gathered, you can only do undergraduate if the job you want has it as a method of entry. Pilot and ACO do not have it as a method of entry. you can see it for yourself
Pilot | Defence Jobs
the methods of entry are written in blue below 'job details'.
Positions like legal officer do have it. You can see here
Legal Officer | Defence Jobs that 'undergraduate' is written in blue below 'job details' (although legal officer is the hardest undergraduate position to get, as there was only 2 people who were successful last year across the whole defence force).
Remember that with most undergraduate positions you need to have completed your 1st year before they except you.
If you want to be a pilot or ACO and go to uni, ADFA is your only option (as far as I know). And you can only do a small number of degrees for those positions (like aviation, engineering and science degrees). You can find a list on the ADFA web site.
If you are young or a school leaver, reading threads on this forums I have learned it is easier to be a pilot if you join through ADFA.
You can find a wealth of information (that money can't buy) about tips on joining the RAAF as a pilot on this thread
http://www.pprune.org/military-aircr...merged-33.html which has been going from 2001 up to today, so you have alot of people who have gone through the whole application proccess and are now pilots in the RAAF giving advice as well as instructors (past and present).
By the way the phone number for DFR is 131902.