PRA ecu in JDM vehicle (JDM EP3/DC5)

Can you use a PRA ecu in a JDM EP3/DC5 in place of the original PRD/PRC ecu ?

Yes you can, however you must disable the primary oxygen sensor in the K manager software and therefore closed loop fuelling will be lost.  You must also use a PRA european calibration as a starting point for tuning.