Ok, now I have an Optus Online account by I stupidly didn't write down my password, nor my favorite movie question.

And I have forgotten both. My account is now locked and says to try again later. Is it possible to go to an Optus store to sort this out?

Nope.

I'd have thought if you called the phone line, and spoke to someone, and proved yourself via their normal info questsions, then they'd be able to reset it? Not so much at a store though, cos they don't do anything at store level.