Is it permissible to supplicate in prayer for returning in time to a specific period of one’s life, and does that invalidate the prayer?

Praying to return to a specific time period is impossible and forbidden, but the prayer itself is not invalidated by it. It is forbidden to supplicate for something impossible, whether by religious law or by custom. The apparent ruling is that the prayer is absolutely valid, regardless of whether the impossible thing is rationally, customarily, or religiously so.