No, you don't need to reapply if you already have an enrolment (before 31 December 2020).
Tuition Fee Relief and Lock-in terms are also available to students with current enrolments. If you enrolled at APC prior to 31 December 2020, and your current enrolment goes beyond 30 June 2021, you will automatically receive up to 4 Lock-in terms of TFR. If your enrolment does not reach 4 terms of study in the lock-in period, you are invited to apply for an extension before 31 December 2020 to take advantage of this offer.