What is the reality of the stories narrated by some Shiites concerning a deceased person performing prayer after his death, the healing of the sick at the tomb of Imam al-Ridha, and the smiles of martyrs in their pictures?

Whoever dies a true death does not return to this world. The evidence for this is Allah's saying: {And behind them is a barrier until the Day they are resurrected} (Quran 23:100), and His saying: {And it is forbidden for a town which We destroyed that they should return} (Quran 21:95). Seeing a deceased person smiling is not a criterion for their state. Seeing the dead while awake is usually fabricated stories or from the deception of devils, as Shaykh al-Islam Ibn Taymiyyah mentioned that devils may appear in the form of the dead to mislead people, and this happens to many who claim to be Muslim and others. As for seeing the Prophet, peace and blessings be upon him, in a dream, it is true, because Satan cannot impersonate him. However, he is not seen while awake with the eye, neither he nor any other deceased person. And Allah knows best.