The liberatus were roman slaves, liberate by their master o who bought they freedom from the state. They usually did not end up in battle but in the administration, often becoming rich and envied; surely not cover in rags and armed with an axe.
The Celtic unit "Norman King" refers to a period almost a 1000 years later; even if transferred to a Britons faction like the later game.
Gallics and Celts warriors never used horned helmet in battle, only rarely during ceremony. Thank to mutual cultural exchange the were beginning the look similar with their Romans, italics, Iberics and north Africans contemporary.
Although correctly called hastatus, princeps and equites, the aspect of roman soldier is clearly inspired by the later 1st or 2nd century imperial armies.
Both Syracuse and Messana were Greek cities. Messana was occupied prior to the first Punic war by various southern Italians mercenary who asked for the support to Rome. Syracuse, initially allied with Rome, was later laid under siege till 202 b.c. and conquered after fiercely defending itself, aided by the famous Archimede who died at its fall.