Do the verses on breastfeeding mentioned in the Qur'an pertain to those who carried and gave birth at six months, with the completion of breastfeeding being at 30 months, and are all gestation periods measured by this, such that for one who gave birth at nine months, the sufficiency of breastfeeding for the infant would be 21 months (calculated as 30-9=21), or are the two full years referred to in Surat Al-Baqarah measured from the birth of the child after the completion of the pregnancy, not from the age of the pregnancy?

The verse from Surat al-Baqarah indicates that the original duration for breastfeeding is two full years for those who wish to complete the suckling. This is not mandatory, but rather the completion. It is permissible to suffice with less than that if the infant is not harmed.

Scholars have deduced from this verse that the forbidden suckling is that which occurs within the two years, because breastfeeding is completed upon their expiry, and nothing thereafter is considered [suckling]. This is the view of the majority of scholars.

As for the verse from Surat al-Ahqaf, it mentions the minimum period of gestation (six months), and it provides a great benefit in establishing the lineage for the husband if the child is born after six months of marriage.