Here's what happened:
* The Age Line: They tried to circumvent the age line put in place by the Ministry of Magic to prevent underage wizards from competing in the Triwizard Tournament. However, their attempt was quickly thwarted.
* Their Age: Their attempts to fool the Goblet were likely due to their desire for adventure and the possibility of being chosen as champions, despite being underage.
While they were known for their pranks and mischief, they didn't specifically try to fool the Goblet itself. Their actions were more about trying to bypass the age restriction in place.