This is some information on your third coin. I can't make out the complete mintmark but there should be a dot in crescent after the dot PLG. Your coin is from Lugdunum, which is now Lyon, France. Lugdunum was named after the Celtic sun-god, Lug or Lugh.
Constantine I
A.D. 323-4
CONSTANTINVS AVG; laureate head right.
SARMATIA DEVICTA; [On the occasion of Sarmatia being conquered] Victory advancing right, holding trophy, palm branch, spurning captive seated on ground to right, C in left field.
In exergue dot PLG (dot in crescent)
RIC VII Lyons 222
This coin refers to a major victory over the Sarmatians in A.D. 322. This, however, was a big reason for the second civil war with Licinius, since the territory that Constantine fought the Sarmatians in was under the control of Licinius.
"When Constantine learned that the Sarmatians, who live near Lake Maeotis, had sailed across the Danube and were pillaging his territory, he led his army against them...he killed many, took more prisoners and put the rest to flight." Zosimus 2:21