What is the ruling on reciting the Quran in the graveyard during burial and at home during vigils with the deceased's family, and what is the ruling on group dhikr with admonitory poems to prevent idleness and backbiting?

Reading the Qur'an in the graveyard during burial or at the house of the deceased is not from the guidance of the Prophet (peace be upon him) nor the righteous predecessors (Salaf). The Salaf disliked gathering at the family of the deceased and considered it a form of unlawful wailing (niyahah). If a reciter reads the Qur'an and dedicates its reward to the deceased, it will reach them, Allah willing. As for mentioning admonitions and beneficial poems, it is better than idle talk. However, gathering for it at the family of the deceased, as if it were a sunnah or a requirement, is not originally legislated.