Welcome to PPRuNe
Regarding your post, don't you think it's a little irrelevant? If you want the job, you're going to need to apply and find out whether or not they treat you differently in the interview.
I'm sure that most OASC board members would pick up on the fact that this is "take 2" for you and I'd expect some slightly awkward questions. Why did you apply for a 6th Form Scholarship if you didn't think you were mature enough to commit to the length of service, or hack university? Why should they believe you've changed? Why do you think you deserve a second chance, when there are dozens of applicants who would have chewed their and your arms off for the opportunity you had?
You'll be treated as a normal applicant; they won't reject you out of hand because of this, but don't be surprised if it comes up in conversation. If I were you I'd get some spectacular answers together for questions like those above.
As far as aptitude tests go, if I remember right the majority of the tests are time limited. Hence you'll resit some, but not others.