When did the incident of Abd al-Muttalib's vow occur, and what is the correct narration regarding the ages of Hamza and Al-Abbas compared to the Prophet, especially with what has been reported about Al-Abbas's participation in the vow incident?

The gist of the Fatwa:

Al-Abbas and Hamza, may Allah be pleased with them, were born two or three years before the Prophet, peace be upon him. The story of Abd al-Muttalib's vow to sacrifice one of his sons is well-known and its chain of narration (isnad) is authentic. As for the presence of Al-Abbas and Hamza at the time of the attempted sacrifice of Abdullah, its chain of narration is weak and its text (matn) is denounced (munkar); because Ibn Ishaq narrated it with the phrase "as they mention," without a connected chain of narration. Moreover, the majority of biographers state that the number of Abd al-Muttalib's sons was more than ten (twelve or thirteen), and that Al-Abbas and Hamza were younger than Abdullah, the Prophet's father, and had not even been born at the time of the vow incident.