From the way you explained it here and you also know how to use the STAR approach, i think your chances are still high.

My experience with the ACN interview process was good. They were very efficient, so the whole application process took me about 2 weeks only.
Basically, they are quite structured in their hiring process. Just like what the company does. haha!
As far as I know, the 2nd interview is the most crucial part in your application. The 3rd one is just a formality interview, a closing interview whereby you'll meet their partner. It was also quite a nice chat with the partner, just a casual chat and discussion about your expectation at ACN.

Goodluck to you pacmann!