I am happy to provide answers to your questions, though it is sad that your church has left you ignorant of them.
Having therefore, brethren, boldness to enter into the holiest by the blood of Jesus, (Hebrews 10:19)
The NT church was spiritually located in Heaven, where those who are adopted by God being made accepted in the Beloved (on His account) have their citizenship and are made to sit together with Christ, by whose sinless shed blood they have immediate access into the holy of holies in Heaven, and will go to be with Christ at death or His return, which ever comes first.
Having predestinated us unto the adoption of children by Jesus Christ to himself, according to the good pleasure of his will, To the praise of the glory of his grace, wherein he hath made us accepted in the beloved. (Ephesians 1:5-6)
And hath raised us up together, and made us sit together in heavenly places in Christ Jesus: (Ephesians 2:6)
For our conversation is in heaven; from whence also we look for the Saviour, the Lord Jesus Christ: Who shall change our vile body, that it may be fashioned like unto his glorious body, according to the working whereby he is able even to subdue all things unto himself. (Philippians 3:20-21)
We are confident, I say, and willing rather to be absent from the body, and to be present with the Lord. (2 Corinthians 5:8)
Then we which are alive and remain shall be caught up together with them in the clouds, to meet the Lord in the air: and so shall we ever be with the Lord. (1 Thessalonians 4:17)
This the body of Christ, (Colossians 1:18) is the one true church to which He is married, (Ephesians 5:25) the "household of faith," (Galatians 6:10) for it uniquely only and always consists 100% of true believers, and which spiritual body of Christ is what the Spirit baptizes ever believer into, (1Co. 12:13) while organic fellowships in which they express their faith inevitably become admixtures of wheat and tares, with Catholicism and liberal Protestantism being mostly the latter.
However, as for the organic visible fellowships in which the NT believers met, usually along with some tares, these were located in various cities mentioned in the only wholly God-inspired and faithful substantive record of what that NT believed (see further below).
And who exactly were its leaders?
The apostles, as well as pastors and "certain prophets and teachers; as Barnabas, and Simeon that was called Niger, and Lucius of Cyrene, and Manaen, which had been brought up with Herod the tetrarch, and Saul" (Acts 13:1) who obeyed God in sending Paul on mission. And who in turn was the primary active leader of the NT church, laboring more than all, (1 Corinthians 15:10) while before him (married) Peter was the main active pastor and missionary and who first preached the evangelical gospel of salvation by effectual faith to Jews and Gentiles , (Acts 2:14-39; 10:36-47; 15:7-10) who later exercised a general pastoral role from Jerusalem, (1 Peter 1:1) who along with James (whom Paul names first) and John Paul refers to as pillars in Galatians 2:9.
And which are the documents wherein these leaders set forth their teachings about the gospels?
These are in the Scripture, which you must have heard read, if briefly, especially Acts thru Revelation, which best show us how they believed the prior revelation, and which books make up the bulk of the New Testament. But in which distinctive Catholic teachings are not manifest.
And, since generalized statements are usually mere conjecture, if you can, please provide specific and verifiable answers, i.e., names, locations, documents, dates, etc.
These are supplied by that authoritative source, consistent with the fact that God manifestly made writing being what God manifestly made His most-reliable means of authoritative preservation. (Exodus 17:14; 34:1,27; Deuteronomy 10:4; 17:18; 27:3,8; 31:24; Joshua 1:8; 2 Chronicles 34:15,18-19, 30-31; Psalm 19:7-11; 102:18; 119; Isaiah 30:8; Jeremiah 30:2; Matthew 4:5-7; 22:29; Luke 24:44,45; John 5:46,47; John 20:31; Acts 17:2,11; 18:28; Revelation 1:1; 20:12, 15;
And thus as abundantly evidenced , as written and established, Scripture became the transcendent supreme standard for obedience and testing and establishing truth claims as the wholly Divinely inspired and assured Word of God;
Thus the veracity of even apostolic oral preaching could be subject to testing by Scripture; (Acts 17:11) even though men such as the apostles could speak as wholly inspired of God and also provide new public revelation thereby (in conflation with what had been written), yet neither of popes and councils do.
As for historical dates of composition and a summary of contents, see here for one, by the grace of God..
Hope this helps. http://peacebyjesus.net
Hope this helps.
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It doesn’t, because quoting Scripture and those who wrote it doesn’t answer my questions. And you failed to identify any writings of the other people you mentioned or where exactly this New Testament church was established, although I suppose that would be difficult since today those who claim to belong to that church commonly state that it has always been “invisible”!