What is the authenticity of the interpretation of the Hadith which indicates the proximity of the Hour with the death of the young boy, and does that mean that the Hour will commence before he grows up?

The Hadith (definition) indicates that "your Hour" refers to the death of those addressed, and not the major Day of Judgment. Al-Qadi and Al-Kirmani explain that the intention is the end of the era of those addressed or their death, in order to urge them to perform good deeds before it is too late. As for Al-Raghib Al-Isfahani, he clarified that the term "Hour" is applied to three types: the Greater (the Day of Judgment), the Middle (the death of the people of an era), and the Lesser (the death of an individual).