Answer: In the story "Briar Rose," the last prince was the first person to be able to enter the hedge of thorns because he was the bravest of all the princes who had tried to get through.
Explanation: The text suggests that the hedge of thorns was an obstacle that required great bravery to overcome. The previous princes who attempted to enter the hedge may not have been as courageous as the last prince. They might have been scared or hesitant to face the challenge.
The story also does not mention anything about 100 years passing and the curse being over as a reason for the last prince's success. Additionally, there is no mention of the hedge losing some of its thorns and becoming less thick.
Therefore, based on the information provided in the question and the context of the story, the most reasonable explanation is that the last prince was able to enter the hedge of thorns because he was the bravest among all the princes who had attempted to do so.