Here we see Paul quote this OT passage about YHWH and apply it to Jesus who is the one and only Lord according to the N.T. As Paul says He is the same Lord who is Lord of all. Jude calls Him our Only Lord and Paul in 1 Cor 8:6 says He is our One Lord.
Yes, Paul quotes the Old Testament verse Joel 2:32, which refers to God Yahweh. However, he's not implying that it is referring to Jesus rather than Yahweh. Verse 11:
(11) For the scripture saith, Whosoever believeth on him shall not be ashamed.
is referring to Isaiah 28:16 (Therefore thus says the Lord Yahweh, “Behold, I lay in Zion for a foundation a stone, a tried stone, a precious cornerstone of a sure foundation. He who believes shall not act hastily.), which Paul also refers to in Romans 9:33 (KJV):
(33) As it is written, Behold, I lay in Sion a stumblingstone and rock of offence: and whosoever believeth on him shall not be ashamed.
That is referring to Jesus. But Paul's message here is concerning the Jews, and Paul's desire that they may be saved, and verses 12 and 13 are referring to the God of Israel, not Jesus. He says that the God of Israel, Yahweh, is the God of all mankind, repeating what he had written earlier in Romans 1:16 (WEB):
(16) For I am not ashamed of the Good News of Christ, because it is the power of God for salvation for everyone who believes; for the Jew first, and also for the Greek.
So a person must confess Jesus is YHWH(Lord) to be saved. Confess means to agree with so the person confessing Jesus is Lord is in agreement that He is YHWH. Whoever will call upon the name of the Lord ( YHWH) will be saved.
No, he's not saying that. He quotes Joel and he is saying that to be saved we must all call on the name of YHWH and confess that Jesus is our Lord, as God has appointed him to be our Lord (Matthew 28:18). He finishes up his referring to the Jews with:
Romans 10:18-21 (WEB):
(18) But I say, didn’t they hear? Yes, most certainly, “Their sound went out into all the earth, their words to the ends of the world.”
(19) But I ask, didn’t Israel know? First Moses says, “I will provoke you to jealousy with that which is no nation. I will make you angry with a nation void of understanding.”
(20) Isaiah is very bold, and says, “I was found by those who didn’t seek me. I was revealed to those who didn’t ask for me.”
(21) But as to Israel he says, “All day long I stretched out my hands to a disobedient and contrary people.”
and continues in chapter 11 with:
(1) I ask then, did God reject his people? May it never be! For I also am an Israelite, a descendant of Abraham, of the tribe of Benjamin.
The "Good News of Christ", the Gospel, is not that Jesus is YHWH, it's that:
Romans 8:2-3 (WEB):
(2) For the law of the Spirit of life in Christ Jesus made me free from the law of sin and of death.
(3) For what the law couldn’t do, in that it was weak through the flesh, God did, sending his own Son in the likeness of sinful flesh and for sin, he condemned sin in the flesh;
Romans 5:1-11 (WEB):
(1) Being therefore justified by faith, we have peace with God through our Lord Jesus Christ;
(2) through whom we also have our access by faith into this grace in which we stand. We rejoice in hope of the glory of God.
(3) Not only this, but we also rejoice in our sufferings, knowing that suffering produces perseverance;
(4) and perseverance, proven character; and proven character, hope:
(5) and hope doesn’t disappoint us, because God’s love has been poured out into our hearts through the Holy Spirit who [which/that] was given to us.
(6) For while we were yet weak, at the right time Christ died for the ungodly.
(7) For one will hardly die for a righteous man. Yet perhaps for a righteous person someone would even dare to die.
(8) But God commends his own love toward us, in that while we were yet sinners, Christ died for us.
(9) Much more then, being now justified by his blood, we will be saved from God’s wrath through him.
(10) For if, while we were enemies, we were reconciled to God through the death of his Son, much more, being reconciled, we will be saved by his life.
(11) Not only so, but we also rejoice in God through our Lord Jesus Christ, through whom we have now received the reconciliation.