Is a person held accountable in their grave, and what is the authenticity of the narration about the dream of Umar ibn Al-Khattab which stated: "My Throne almost collapsed, had I not found my Lord Forgiving, Merciful"?

The narrative of seeing Umar in a dream is weak in its chain of transmission and text, and its meaning suggests that the throne indicates humiliation and perdition. As for the reckoning in the grave, several hadiths allude to it, such as the servant being judged first for urine, and that the torment of the grave is due to backbiting, slandering, and urine. Some scholars have mentioned that the grave is the first stage of the Hereafter, and in it, the servant is held accountable for the preliminaries of Allah's rights and the rights of people, such as purification for prayer and backbiting as the simplest forms of harm. The first thing a servant will be asked about in the grave is their prayer.