Sure, you can ask.
No, the preliminary round isn't for your first preference.
No, you're not stupid!
Preliminary Round
Some institutions make a limited number of offers in the Early and Preliminary rounds.
Offers in these two rounds are generally made to applicants who have deferred, applicants who are selected predominantly on criteria other than an Australian Year 12, and international fee-paying applicants. Only applicants that are made an offer will be sent a letter.
Main Round
Most offers are made in the Main Round at which time institutions try to make sufficient offers to fill the places available. In the 2003 admissions period, institutions made approximately 48 000 offers in the Main Round. A letter will be sent to all applicants whether or not they have received an offer in this round.
More detail:
Offer Rounds
http://www.uac.edu.au/apply/offer_rounds.html