Are the mentioned customs of distributing bread, fruit, and cakes to the poor at gravesides on specific days (15th and 40th) and frequent visits permissible in Islamic law, and what is the correct practice regarding offering condolences and visiting graves, and is it preferable to give charity there at the graves or in the city?

The origin of offering condolences and visiting graves is commendable. However, the fortieth-day commemoration of the deceased and preparing food for it is an innovation (bid'ah) that must be abandoned. Had it been good, the Prophet, peace and blessings be upon him, and his companions would have preceded us to it. The Prophet, peace and blessings be upon him, said: "Beware of newly invented matters, for every newly invented matter is an innovation, and every innovation is a misguidance." As for giving charity on behalf of the deceased, it is legislated and its reward benefits them. However, performing it at graves and believing that it has a special merit is an innovated matter.