That Kingdom already exists and has existed since before the foundation of the world. Hence it cannot be some future millennial earthly kingdom.
I could answer the “such as” question if there were enough hours in the day, however I can mention a few things: Praying to the saints, the assumption of Mary, Purgatory, confessing sins to a priest, Christ in the tabernacle in the church, the pope, sacrifice of the mass, succession of the apostles, hierarchy in the RCC, the RCC necessary for salvation. There are so many things based on tradition, they are too many to count which I don’t have time to write. The next statement, " and you know that because you heard it through…word of mouth" is not the way I received it. I received it from the written word of God. Blessings.
Rom. 10:8 - the Word is near you, on your lips and in your heart, which is the word of faith which is preached (not just written).
Rom. 10:17 - faith comes by what is “heard” (not just read) which is the Word that is “preached” (not read). This word comes from the oral tradition of the apostles. Those in countries where the Scriptures are not available can still come to faith in Jesus Christ.
1 Cor. 15:1,11 - faith comes from what is “preached” (not read). For non-Catholics to argue that oral tradition once existed but exists no longer, they must prove this from Scripture. But no where does Scripture say oral tradition died with the apostles. To the contrary, Scripture says the oral word abides forever.
Gal. 1:11-12 - the Gospel which is “preached” (not read) to me is not a man’s Gospel, but the Revelation of Jesus Christ.
Eph. 1:13 - hearing (not reading) the Word of truth is the gospel of our salvation. This is the living word in the Church’s living tradition.
Col. 1:5 - of this you have “heard” (not read) before in the word of truth, the Gospel which has come to you.
1 Thess. 2:13 - the Word of God is what you have “heard” (not read). The orally communicated word of God lasts forever, and this word is preserved within the Church by the Holy Spirit.
2 Tim. 1:13 - oral communications are protected by the Spirit. They abide forever. Oral authority does not die with the apostles.
2 Tim. 4:2,6-7 - Paul, at the end of his life, charges Timothy to preach (not write) the Word. Oral teaching does not die with Paul.
Titus 1:3 - God’s word is manifested “through preaching” (not writing). This “preaching” is the tradition that comes from the apostles.
1 Peter 1:25 - the Word of the Lord abides forever and that Word is the good news that was “preached” (not read) to you. Because the Word is preached by the apostles and it lasts forever, it must be preserved by the apostles’ successors, or this could not be possible. Also, because the oral word abides forever, oral apostolic tradition could not have died in the fourth century with all teachings being committed to Scripture.
2 Peter 1:12, 15 - Peter says that he will leave a “means to recall these things in mind.” But since this was his last canonical epistle, this “means to recall” must therefore be the apostolic tradition and teaching authority of his office that he left behind.
2 John 1:12; 3 John 13 - John prefers to speak and not to write. Throughout history, the Word of God was always transferred orally and Jesus did not change this. To do so would have been a radical departure from the Judaic tradition.
Deut. 31:9-12 - Moses had the law read only every seven years. Was the word of God absent during the seven year interval? Of course not. The Word of God has always been given orally by God’s appointed ones, and was never limited to Scripture.
Isa. 40:8 - the grass withers, the flower fades, but the Word of our God (not necessarily written) will stand forever.
Isa. 59:21 - Isaiah prophesies the promise of a living voice to hand on the Word of God to generations by mouth, not by a book. This is either a false prophecy, or it has been fulfilled by the Catholic Church.
Joel 1:3 - tell your children of the Word of the Lord, and they tell their children, and their children tell another generation.
Mal. 2:7 - the lips of a priest guard knowledge, and we should seek instruction from his mouth. Protestants want to argue all oral tradition was committed to Scripture? But no where does Scripture say this.