The Summa Theologicae on prayers for the dead

The suffrages for the dead (Supplementum, Q. 71). Probably not written or if so only in outline form by St Thomas, but no error is to be found here.

Can suffrages performed by one person profit others?
Can the dead be assisted by the works of the living?
Do the suffrages of sinners profit the dead?
Do suffrages for the dead profit those who perform them?
Do suffrages profit those who are in hell?
Do they profit those who are in purgatory?
Do they avail the children in limbo?
Do they, in any way, profit those who are heaven?
Do the prayer of the Church, the Sacrament of the altar, and almsgiving profit the departed?
Do indulgences granted by the Church profit them?
Does the burial service profit the departed?
Do suffrages for one dead person profit that person more than others?
Do suffrages for many avail each one as much as if they were offered for each individual?
Do general suffrages avail those for whom special suffrages are not offered, as much as special and general suffrages together avail those for whom they are offered?"