Question: I have already registered and went through the interview for AppleOne. I ended up taking another job but am now wanting to use AppleOne again to find another job. Do I need to do the interview and everything all over again?
Answer: If you're returning to the same office, and the same AE is there, reintroducing yourself and making them aware of your availability may be enough. But, I wouldn't be asking if you need to be doing the interview again. I'd be asking if you should, and to that, the answer is probably yes.
If anything has changed or even if it's just been a bit of a while, I'd schedule a new interview just to be sure. The better your relationship with your AE, the more likely they will be to think of you as opportunities present themselves. The interview is your best chance to develop that relationship. So, while the interview does require some time, it positions you for better results working with AppleOne.