Primal Wellspring triggers, copying Narset's Reversal targeting the original Narset's Reversal.
Resolve the copy of Narset's Reversal, copying the original Narset's Reversal targeting Hidden Strings, and returning the original Narset's Reversal to your hand.
Resolve Narset's Reversal, copying Hidden Strings targeting Primal Wellspring and the mana-producing permanent, and returning the original Hidden Strings to your hand.
Resolve the copy of Hidden Strings, untapping Primal Wellspring and the mana-producing permanent.