A:

A latter addition, not in the Roman Typical editions.  See Fr. Petras (below).

The following is from a Liturgikon published prior to the Roman Recension Books - date and printing (and source) are not given.  Fr. John Basarab has indicated that the source is the L'vov Sluzhebnik.

See also comparison texts at:

Communion_prayer-OCS.pdf (application-pdf Object)            <--- pdf   or click to expand image --->        

as noted in

The Byzantine Forum- UGCC Vs. Ruthenian Prayer Before Communion?

CINEAST Archives- Re- New Byzantine Liturgy ( <<< this archive is unfortunately no longer active)

Date: Mon, 12 Oct 1998 23:08:40, -0500
From: SXHV44A_at_prodigy.com (MR DAVID M PETRAS)
Subject: Re: New Byzantine Liturgy

You certainly have a fine ear for liturgical texts.
The section of the Communion Prayer, "O Lord, I believe and profess
that this, which I am about to receive ..." was added into the
Ruthenian Liturgy sometime after the mid-19th century. It was
omitted as a late addition from the approved Roman texts done in the
1940's. I have always thought it was a kind of mild Romanization,
emphasizing the real presence (I say "mild" because CERTAINLY the
Byzantines believe that the eucharist is truly the body and blood of
Christ) in a phrase that would seem more Roman, but I have found it
in a Communion Prayer attributed to St. John Chrysostom, "I also
believe that this is indeed your immaculate Body and that this is
indeed your precious Blood." (Voices in the Wilderness: An Anthology
of Patristric Prayers, translated by Nikolaos S. Hatzinikolaou, Holy
Cross Orthodox Press, 1988, p. 107)

Sharon is mistaken in concluding that you were referring to "We have
seen the true light ... " as you are clearly referring to "May our
lips be filled ...," the more ancient post-Communion hymn. Here
again you have a good ear. The oral tradition of the Ruthenian
Church has a different version than the official Roman version. In
Slavonic, the Roman version reads, " ... bozhestvennym, bezsmertnym,
i zhivotvorjashchim Tajnam ... ," but a variant found only in some
Ruthenian texts is, " ... svjatym, prechistym, i zhivotvorjashchim
Christe tvojim Tajnam ... ." That is, "your holy, pure and life-
creating mysteries, O Christ ... " The word for "pure" is not found
in the usual Slavonic texts, but has been inserted into the new
translation that will be coming out.

In regard to "Na mnohaja lita, Vladyko," it should be noted that this
hymn, "We have seen the true light ..." entered the Liturgy very
late (after the 15th century). In the 16th century, we find it in
the priests' liturgicon, with the preface, "Na mnohaja lita, Vladyko,
" probably because the priest blessed with the gifts just before,
"Save your people, O Lord, and bless your inheritance." This same
text appears in the 17th century Moscovite editions, but in the early
18th century, the phrase "Na mnohaja lita, Vladyko," ("For many years,
O Master") was removed from the priests' liturgicon, because it was
considered to apply only to the bishop. It continued to appear in
Ruthenian (= Ukrainian and Rusin) texts until the 20th century, when
the 1942 Roman edition also removed it, following the Orthodox usage
of reserving it only to the bishop. It has since fallen into disuse,
and we have not restored it in the new translation.

Fr. David Petras