Regarding the Narrator intro:
I think it was more artistic license, but it is true in essence (at least initially). Just to go through each of the characters listed.
Regina knows because she remembers.
Henry doesn’t know, he just believes. He probably knows something really bizarre is going on in the town, but latches onto the fairytale book-based explanation due to its striking similarities. It just happened that the fairytale explanation was the correct one.
Gold, as has been mentioned in off-screen interviews, didn’t know until he heard Emma’s name in Emma’s presence.
August knew, but he never went to storybrooke (presumably) at any point earlier than we saw.
Jefferson knew and was technically in Storybrooke, but he was unable to leave his house (apparently) until sometime after Emma’s arrival. As a result, he had no ability to change anything.
Admittedly, they do make it rather ambiguous in the show, but maybe the producers or the suits later decided to throw viewers a bone by basically giving it away that Regina knew who she was. It still didn’t stop people from wanting to believe that she didn’t remember her past either.