Where is hyparchio used to assert pre-existence? The exact verse please. The only one I can think of is Phil. 2:6 by . The word itself is obviously another Pauline innovation because the only other author besides Paul who uses the word is Luke, not surprisingly and definitely not in the meaning you suggest.
The earliest copy of the letter to Philemon is a fragment dated 3d century otherwise known as Papyrus 87 which contains but a few broken verses. The earliest complete copy of the Epistle to Philemon known is a copy dating to the 7th century (Papyrus 60).
Based on that we can't possibly know if the verse Phil 2:6 was in the original the way it appears in P60 because we do know that manuscripts have been "Christianized" to keep up with the develping doctirnes.
Papyrus 89 (4th century) allegedly contains the letter to Philemon, but to my knowledge that papyrus is a copy of the Book of Hebrews, which was not written by Paul, and is not a collection of Pauline prison letters.
Bingo!
...who, being in the form of God...
huparcho, "existing", referring to the continued state of a thing, with morph meaining the essential attributes as shown in the form, i.e., the essence his nature. Being (uparxwn).
RWP
Existing in the form of God denotes pre-existence, obviously.
Cordially,