What is the religious ruling on playing the daff for men and women, and to what extent is it permissible for a woman to sing in front of non-mahram men, especially given the differing fatwas on this matter?

The two mentioned fatwas do not contradict each other. The first is concerning the ruling on men playing the duff (tambourine), and the second is concerning the ruling on their listening to it. The issue of men playing the duff has an old disagreement among scholars, and most scholars are of the opinion that it is permissible, citing the hadith: "The distinction between lawful and unlawful is sound and the beating of the duff," and the hadith of the young girl. Even with the permissibility, one should not overuse it, whether by playing or listening, and it is preferable to restrict it to appropriate occasions. The argument for the permissibility of listening to a woman's singing based on the incident of the young girl singing in the presence of the Prophet (peace be upon him) is conditioned upon the absence of temptation (fitna), which is often questionable. Moreover, the young girl might have been of a young age, thus precluding any fear of temptation.