You are absolutely correct!
Did the early Christians have the Bible as we know it? No. The Bible as a whole was not compiled until the late 4th century and then it was compiled by a Catholic saint (St. Jerome) at the request of a Catholic pope (St. Damasus). So how were the early Christians saved if they did not possess the entire written "Word of God" to follow His teachings? Well, naturally, they were the Body of Christ and were taught through "oral" teachings by the Church, not by writings.
Is the Bible the sole authority and foundation of truth for Christianity? No, the Church is the "pillar and bulwark of truth" (1 Timothy 3:15) and the final authority (Matthew 18:17). Furthermore, there are traditions to be observed which are on equal footing with Scripture for not everything the Apostles taught or Jesus said, was written down (1 Corinthians 11:2; 2 Thessalonians 2:15; 3:6; John 21:25).
They teach heresies such as transubstantiation
Actually, Christ taught transubstantiation.
"I am the living bread which came down from heaven: if any man eat of this bread, he shall live for ever: and the bread that I will give is my flesh, which I will give for the life of the world. The Jews therefore strove among themselves, saying, How can this man give us [his] flesh to eat? Then Jesus said unto them, Verily, verily, I say unto you, Except ye eat the flesh of the Son of man, and drink his blood, ye have no life in you. Whoso eateth my flesh, and drinketh my blood, hath eternal life; and I will raise him up at the last day. For my flesh is meat indeed, and my blood is drink indeed. He that eateth my flesh, and drinketh my blood, dwelleth in me, and I in him." - John 6:51-56
also teach that one must be a catholic to be saved
The Catholic Church has always taught that salvation is a gift from God (cf. Ephesians 2:8-10) and that men and women must accept that gift through faith.
"Faith is an entirely free gift that God makes to man. We can lose this priceless gift, as St. Paul indicated to St. Timothy: 'Wage the good warfare, holding faith and a good conscience. By rejecting conscience, certain persons have made shipwreck of their faith.' [1 Tim 1:18-19 .] To live, grow and persevere in the faith until the end we must nourish it with the word of God; we must beg the Lord to increase our faith; [Cf. Mk 9:24 ; Lk 17:5 ; Lk 22:32.] it must be 'working through charity,' abounding in hope, and rooted in the faith of the Church. [Gal 5:6 ; Rom 15:13 ; cf. Jam 2:14-26.]"
Catechism Catholic Church
Jesus NEVER taught transubstantiation, otherwise He would have never left the room alive.