HKU BA(Major in Psychology )

First of all, studying in the community college of a HK university does not guarantee admission to the undergraduate programme. For those who study sub-degree or A.dip programme, only the very top student (usually 1-2 per year) and reaches the university admission level can go directly to the undergraduate programme.
Yes, there is mature student admission possibility, but it is under the non-Jupas system .Every year, more than thousands of people applying through the non-Jupas system hoping to be admitted to the university. But usually they give chances to those with outstanding score from overseas or with special talents. As far as I concern, those who get admitted as mature students are studying general courses like Arts in HKU. Hit subject like HKU-BA and CU-psycho is nearly impossible for mature students.
Link for HKU admisison .http://www.hku.hk/admission/ug.htm