Is it permissible to transfer ownership of properties to a sister while retaining the right to usufruct from them, or only a third of them, or to donate them to charities?

Relinquishing property after death is called a will (wasiyyah (definition)). A will in favor of an heir is not valid, and it is not permissible for it to exceed one-third [of the estate]. A will made for an heir is initially unlawful (haram (definition)); however, it becomes valid and enforceable if the other heirs approve it after the death [of the testator]. It is permissible to make a will of one-third or less for a non-heir, such as a sister's children, or for a charitable cause. As for donating or giving charity to a sister or anyone else during one's lifetime, it is permissible, provided that ownership of the donated money is relinquished.