Does supplication for the deceased reach them from any place, and what is the difference between supplicating at the grave and supplicating for them in another place?

A Muslim's supplication for one of the deceased Muslims undoubtedly benefits them. This is what the Ummah has unanimously agreed upon regarding supplication for the deceased in the funeral prayer and after burial. There is no difference between supplicating at their grave or far from it, except that supplicating at the grave includes the virtue of visiting graves, which benefits both the visitor and the deceased.