Here the 1841 British edition omitted the determiner his before demands. The occurrence of “all demands” is definitely unexpected. The subsequent LDS edition (in 1849) restored the his. The his is necessary since the masculine pronoun refers to the demands of justice while the feminine her refers to mercy (“and also mercy claimeth all which is her own”). For two others examples of contrastive his and her, referring respectively to the sun and to the moon, see the discussion under 2 Nephi 23:10 and Helaman 14:20 (both of these involve textual variation between his and her).
Summary: Maintain in Alma 42:24 the his in the phrase “all his demands”.