I understand a writ of possession is complementary to a writ of execution. Under the law, a writ of execution prescribes after a number of years, say 5 years. Supposing the period to execute a judgment of the court has prescribed and the judgment was only partially executed as when for instance possession is yet to be awarded to the winning party, will a writ of possession be legally issued by the court?

By "prescribes", I guess you mean something like "expires"?

Could be. It would depend on the statutes and, especially, upon the civil court rules wherever you are. It's not totally clear what is going on. Someone has a judgment, obtained a writ of execution, levied upon some asset of the judgment debtor, and needs a writ of possession to complete the process? Yes, as I say, it depends.