"Presbyteros" can mean all these things, but in Christian usage its primary meaning is "priest", from which "priest" is derived. "Hieros" is primarily pagan or Hebrew priest. I don't think it was ever used as a Christian priest; got a patristic source?
It does NOT mean some elite group
In Matthew 18 it does, because it makes a disctintion beteween an appeal to a group of fellow believers and the Church as a whole. One meaning is not exclusionary of the other, as indeed, "church" can mean the entirety of the believers as well. Context rules, not the dictionary.
Incorrect on both counts.
In Scripture, Presbuteros is I know of no instance where Presbuteros is translated priest. It derives from presbus which means elder or elderly (old man, old woman) or possibly bishop or overseer, but not priest.
The word translated priest in Scripture is hiereus.
It is used of pagan priests (see Acts 14:13); Jewish priests (Matth 8:4; Luke 1:5; believers (Rev 1:6; 5:10; 20:6 1 Peter 2:5; ); and the New Testament knows nothing of a particular class in the hierarchy of the church which is to offer sacrifices. Such is the duty of all Christians (Romans 12:1; Phil 2:17; 4:18; Hebrews 13:15; 1 Peter 2:5; and finally it is used of Christ Hebrews 5:6; 7:11,15, 17,21 and 7:1.
Archiereus is High priest by the way.
Actually, Alex, ο ιερας does mean priest and in the Christian sense even to this day. But ο πρεσβυτερος also means priest in the Christian sense. BOTH of them imply an ordained office. Protestants often misinterpret, through their pride, +Paul's phrase "the priesthood of all believers" to mean that the office of "priest" is some sort of fraud. This is not what the fathers taught at all and such an interpretation would seem to fly in the face of +Paul's own actions. +Peter of Ravenna, called Chrysologos, who was a bishop in the 5th century wrote:
"I appeal to you by the mercy of God. This appeal is made by Paul, or rather, it is made by God through Paul, because of God’s desire to be loved rather than feared, to be a father rather than a Lord. God appeals to us in his mercy to avoid having to punish us in his severity.
Listen to the Lord’s appeal: In me, I want you to see your own body, your members, your heart, your bones, your blood. You may fear what is divine, but why not love what is human? You may run away from me as the Lord, but why not run to me as your father? Perhaps you are filled with shame for causing my bitter passion. Do not be afraid. This cross inflicts a mortal injury, not on me, but on death. These nails no longer pain me, but only deepen your love for me. I do not cry out because of these wounds, but through them I draw you into my heart. My body was stretched on the cross as a symbol, not of how much I suffered, but of my all-embracing love. I count it no less to shed my blood: it is the price I have paid for your ransom. Come, then, return to me and learn to know me as your father, who repays good for evil, love for injury, and boundless charity for piercing wounds.
Listen now to what the Apostle urges us to do. I appeal to you, he says, to present your bodies as a living sacrifice. By this exhortation of his, Paul has raised all men to priestly status.
How marvellous is the priesthood of the Christian, for he is both the victim that is offered on his own behalf, and the priest who makes the offering. He does not need to go beyond himself to seek what he is to immolate to God: with himself and in himself he brings the sacrifice he is to offer God for himself. The victim remains and the priest remains, always one and the same. Immolated, the victim still lives: the priest who immolates cannot kill. Truly it is an amazing sacrifice in which a body is offered without being slain and blood is offered without being shed.
The Apostle says: I appeal to you by the mercy of God to present your bodies as a living sacrifice. Brethren, this sacrifice follows the pattern of Christ’s sacrifice by which he gave his body as a living immolation for the life of the world. He really made his body a living sacrifice, because, though slain, he continues to live. In such a victim death receives its ransom, but the victim remains alive. Death itself suffers the punishment. This is why death for the martyrs is actually a birth, and their end a beginning. Their execution is the door to life, and those who were thought to have been blotted out from the earth shine brilliantly in heaven.
Paul says: I appeal to you by the mercy of God to present your bodies as a sacrifice, living and holy. The prophet said the same thing: Sacrifice and offering you did not desire, but you have prepared a body for me. Each of us is called to be both a sacrifice to God and his priest. Do not forfeit what divine authority confers on you. Put on the garment of holiness, gird yourself with the belt of chastity. Let Christ be your helmet, let the cross on your forehead be your unfailing protection. Your breastplate should be the knowledge of God that he himself has given you. Keep burning continually the sweet smelling incense of prayer. Take up the sword of the Spirit. Let your heart be an altar. Then, with full confidence in God, present your body for sacrifice. God desires not death, but faith; God thirsts not for blood, but for self-surrender; God is appeased not by slaughter, but by the offering of your free will."
As we can see, the priesthood of all believers is a term which describes what we are doing when we die to the self and advance in theosis.