Can the hadith of breaking Al-Rabee's tooth for the young girl and the Prophet's saying, "O Anas, the Book of Allah is Al-Qisas (retribution)," and his saying, "Indeed, among Allah's servants are those who, if they were to swear by Allah, He would fulfill it for them," be considered evidence for excusing by ignorance?

It has not been made clear that the aforementioned Hadith (definition) indicates excuse by ignorance. Scholars have stated that the words of Anas (may Allah be pleased with him): "By Him who sent you with the truth, her incisor will not be broken," were not an objection to the Prophet (peace be upon him), but rather an anticipation and hope for Allah's grace to satisfy her opponent and forgive her, seeking Allah's pleasure. This is why the Prophet (peace be upon him) said: "Indeed, among the servants of Allah are those who, if they swear by Allah, He will fulfill their oath," when the people accepted the blood money, which indicates that Anas was not ignorant of the ruling.