[1] This type of divorce is called zihār: a common practice in Arabia before the Prophet (ﷺ). If someone declared his wife as unlawful for him as the zahr (back) of his mother is unlawful for him, his wife would be divorced. Islam abolished this divorce. Allah says: “As for those among you who divorce their wives by likening them to their mothers, they are not their mothers; their mothers are none but those who gave birth to them.” See 58:2.
[2] Adoption of a child or an orphan is not permissible by ascribing the child to other than their real parents. Whereas, it is permissible for one to sponsor a child or host them in their home and care for them as they care for their own children, except for legal matters.