What is the religious stance on spiritualists and summoning spirits? Can summoned spirits answer scientific questions or perform surgical operations? Can the names of some living spiritualists be mentioned?

No one among people can summon the spirit of the deceased, because spirits, after departing from bodies, transition to the realm of Barzakh (definition). It is Allah Almighty who takes the souls and retains them. What the "spiritualists" claim is either outright lies, psychological and scientific tricks, or the use of jinn and devils, who might be the Qareen (companion jinn) that takes the form of the deceased and answers questions with their abilities. Therefore, it is not permissible to claim to summon the spirits of human beings or to invoke jinn and devils.