Hi,
You should talk to your business and get the requirement- once year end activities are completed for the last year of last period(12) and new period opened(01) for Current(new) Year : how and why posting required for previous year of previous period at present date of Current(new) Year?
If allowed- you do setting in OB52 to allow posting previous year of previous period and MMRV setting for posting allowed for current period & current minus one period.
Regards,
Biju K