✔ 最佳答案
In answering your questions, I am based on every information you have made available.
It is not a good plan at all.
If your ultimate goal is Higher Diploma in Interior Design from HKOU. You should simply focus on the admission of this program.
As you have no HKALE result, the easiest (and cheapest) way is Yi Jin Diploma, focusing Interior Design from HKOU.
By completing Yi Jin, even you decide not to continue, you will still end up with an academic qualification that you can claim similar to Form 7 graduation in the past.
Beside - either diplomas you have suggested do not really increase your chance of admission.