1) How did Nicholas get the better of his aunt when the other children set off on the expedition?

Nicholas get the better of his aunt by defying her. While the aunt hopes Nicholas will cry at being left out, in an instance of situational irony he defies her expectations by laughing at the misfortune of his cousin, who scraped her knee when climbing into the carriage.

Nicholas continues to defy his aunt’s authority by mischievously informing her—but only once it is too late—that his brother Bobby’s boots were tied too tight. In retaliation for Nicholas’s smugness, the aunt adds an additional punishment to his grounding: He is not allowed to enter the gooseberry garden. Nicholas acts as though he is dismayed by the rule, and makes sure to manipulate his face into a look of stubborn defiance.

The look of obstinacy convinces Nicholas’s aunt that he will try to defy her authority yet again, if only because she has expressly forbidden him from entering the gooseberry garden. She sets up an observation position among the flowerbeds, from where she can catch Nicholas when he attempts to sneak into the gooseberry garden. But she doesn’t realize Nicholas has other plans.