Purchasing Period Closing

 Hi  Team,

We are unable to close the Purchasing and inventory period every month end  due to some PRs unable reserve the fund.

We would like to keep  the purchasing period and Inventory period for while and then close. not immediately after the month end.

Also, we have worried about actual entries coming from cost management user should not be deliver good on  backed date GL date.

How to avoid back dated receipt in the cost management/Receiving/Delivery.

Is there any profile option  available for this..

Please advise

Thanks