What is the ruling on someone who performed the stoning of the Jamarat, circumambulated (Tawaf), and performed the ritual of Sa'i, but forgot to shave or cut their hair before exiting the state of Ihram?

There is no penalty for one who wears his clothes before shaving, as long as he has performed the throwing (of pebbles), circumambulated the Ifadah Tawaf, and performed the Sa'i.

As for one who forgets to shave and believes his Hajj is complete, then remembers it, there is a detailed ruling for him in Fatwa No. 47186.

Shaving is preferred over shortening for men.