What is the ruling on praying at graves, and will there be intercession for anyone on the Day of Resurrection other than Prophet Muhammad (peace be upon him)? What is the evidence for that?

Prayer concerning graves is divided into two categories: The first is praying to the occupant of the grave, which is major shirk (polytheism). The second is praying to Allah within a graveyard, which encompasses several rulings: Funeral prayer performed at a grave or in a graveyard is permissible. However, performing other prayers (non-funeral prayers) in a graveyard is invalid, due to the prohibition of the Prophet (peace be upon him) and because it could become a pretext for worshipping graves. As for praying towards a graveyard or a grave, it is forbidden, unless there is a barrier, such as a wall.

Regarding intercession (shafa'ah): The Prophet (peace be upon him) and other believers will intercede, and intercession has two conditions: Allah's permission for the intercessor, and His contentment with the one being interceded for. The imagined intercession that idol worshippers believe in is invalid. And seeking intercession from the Prophet (peace be upon him) after his death is not permissible.