As the sheriff pulls up to talk to Emma, the car number on his patrol car is 02. Since he is a one-man department, there would be no need to have two patrol cars.
At Cinderella's wedding festival, colored fireworks are shown. This type of firework was not invented until the 1830's, which was well after the time when this took place. However, this is in the Enchanted Forest, a fantasy realm where it is perpetually medieval.
When Emma leaves the apartment to go looking for Ashley, she and Henry walk down the streets of Storybrooke, toward Emma's car. As Emma says, "Because I know", in the background, you can see a business called Steveston WineMakers. Steveston is the name of the Canadian town which doubles as the town of Storybrooke on Once Upon a Time.
As Mr. Gold bangs his head on the table after being spritzed with pepper spray, you can see that one performing this action is Robert Carlyle's stunt double, and that the stuntman merely hits the table with his hands.
Emma says she had a baby at 18, but on her 28th birthday in the first episode Henry was already ten years old. She must have had him at 17.