Is it obligatory to repeat the prayer for the deceased upon whom the absent funeral prayer (Salat al-Gha'ib) was performed, after their bodies have been found, and if it is obligatory, should it be before or after burial?

There is no objection to praying over the deceased after burial for those who missed the prayer, provided that the one performing the prayer was eligible to pray over the deceased at the time of burial. The absentee prayer (Salat al-Gha'ib) is sufficient if it is impossible to reach the deceased, such as one hidden by disbelievers. Ibn Hajar al-Haytami stipulated the permissibility of the absentee prayer if it is difficult to be present at the deceased's location due to the large size of the town. It is permissible to repeat the prayer over the deceased before and after burial. As for the martyr of battle, no prayer is performed over him; rather, he is buried with his blood, without ablution or prayer. What is reported about the Prophet, peace and blessings be upon him, praying over them was a supplication, not a funeral prayer.