Must the children return the house to their mother after she had gifted it to them, on the pretext that this is a will from her that must be carried out, and that failure to do so will expose her to torment?

A will in favor of an heir is not permissible in Islamic law and is not enforceable unless the other heirs agree to it, such as a father willing the house to his wife. As for the mother's relinquishment of this house to her male children only, it contradicts the command of the Prophet, peace and blessings be upon him, to be just among children in giving gifts. The mother has the right to revoke her unjust gift, and the children must obey her if she decides to do so. The children must ensure that their sisters receive their rightful share.