What are the grounds for invalidating or terminating an adoption?

Adoption is the legal creation of a parent-child relationship between persons not so related by birth — the adoptive child's full filiation with the adoptive family, with the corresponding severance from (or modification of) the birth family's legal ties. The purposes: lineage-and-succession (the son-adoption of the shastric world — dattaka, the Hindu law's religious institution for funeral rites and lineal continuation); child welfare (the modern turn — orphaned-and-abandoned children's family placement); and the childless couple's parenthood. Nepal's journey: the religious dattak-adoption (son-only, sacramental) → the Muluki Ain's adoption chapter (the son-adoption's codification; daughters excluded) → the Children's Act 2075 and the Civil Code 2074: adoption as a child-centred civil institution — daughters adoptable, welfare-and-registration centred, inter-country adoption controlled.