Is it permissible to expand a mosque towards the Qibla, if it becomes too small, and onto land where the dead are buried, knowing that the mosque is older than the cemetery? And what is the ruling of the Imams on this matter?

The default is the obligation to respect the grave of the deceased and not to exhume it or build upon it, according to the Prophet, peace and blessings be upon him: "Breaking the bone of a dead person is like breaking it when he is alive." The grave is a confinement for its occupant; it should not be walked upon or exhumed except out of necessity. If the aforementioned graves have not disintegrated or something remains of them, then it is not permissible to expand the mosque over them. However, if they have completely disintegrated and no trace of the deceased remains, then it is permissible to build the mosque over them.