How can a person instruct their family to abandon practices that contravene the Sunnah after their death, such as designating mourning days beyond the permissible three, or bringing a female Quran reciter with loudspeakers, or delaying burial to await relatives, or tombs that do not conform to the Sunnah, and what is the appropriate wording for such a will?

Sitting for condolences, gathering for them, specifying days for them, and bringing someone to recite the Qur'an are all newly introduced innovations (bid'ah). A woman's voice is not 'awrah (private/uncovered) unless it involves softness in speech or a seductive tone. Her recitation of the Qur'an in the presence of non-mahram men is disliked for fear of temptation (fitnah). Delaying the burial of the deceased is permissible for a strong need, as long as there is no fear of the body decomposing. It is disliked without a need. An exception is made for someone who died suddenly, or due to collapse, or drowning, in which case delaying the burial is necessary to confirm death. Transporting the deceased from one country to another is permissible for a legitimate purpose, provided there is no fear of disrespecting the deceased. As for writing a will to family and relatives enjoining them to adhere to the Sunnah and avoid innovations and forbidden acts, this is a form of enjoining good and forbidding evil and absolving oneself of responsibility, especially if it is known or strongly suspected that they are engaging in innovations. The will can also be by enjoining them to good and forbidding them from evil, and clarifying the truth to them through speech during life, or by writing a concise statement that includes this.