Is a blood-sacrifice incumbent upon one who intended 'Umrah and passed the Miqat without reciting the Talbiyah, and wore the Niqab out of forgetfulness?

There must be a distinction made between the intention to enter into the ritual (Ihram (definition)) and verbalization and talbiyah (definition). If you had intended to enter into Umrah (definition) before passing the Miqat (definition), then there is no harm in omitting the verbalization and talbiyah, as they are a recommended Sunnah (definition) and not obligatory. However, if you did not intend Ihram at all until after passing the Miqat and did not return to it, then you owe a Dam (sacrificial offering) to be slaughtered and distributed among the poor of the Haram (definition), for neglecting the obligation of Ihram from the Miqat. As for forgetting to remove the niqab after Ihram, there is no consequence for it, because one who wears sewn clothing out of forgetfulness does not owe a Dam.