Hi,
You can use t.code;MB1B with 343 or 349 movement type to remove blocked stock.
To post document in previous period,then use in t.code: MMRV and see which period is open for your company code and specially see back posting is allowed or not, if back posting not allowed,select check box and save.
After setting in t.code: MMRV, you can post in previous period by using t.code;MB1B with 343 or 349 movement type.
NOTE:
343 Transfer posting blocked stock - unrestricted-use stock
349 Transfer posting blocked stock - stock in quality inspection
Regards,
Biju K