Do you know anything about the validity of the Didache, or the supposed non-canonical teachings of the apostles?
From what I can find, parts of The Didache can be dated back to the first century. Some parts were added over the next two to three hundred years. It was never seriously considered part of the canon of scripture, though some say this was because of literary style rather than content.
For the most part it appears to agree with what we have in the Bible. In places it directly quotes scripture. The first part (which deals with how to live) appears very close to the Bible.
The last part (dealing with the government of the church) does appear to show the governance of the first century church, before congregations stopped being autonomous. Bishops still mean elders, and not a head over a group of churches or elders.
On the other hand, there is some evidence of later additions. Scholars of such things may point out different things. The one thing I most quickly noticed was that The Didache, as we have it, allows pouring in place of immersion under certain circumstances, where the clear teaching of the Bible is that baptism is immersion only. The understanding of the church for many years was that one is immersed for forgiveness of sins. This shows how quickly such things can enter the doctrine of the church. Satan works quickly when he has to.
Another thing I noticed was that The Didache requires taking the Lord’s Supper on “the Lord’s Day.” Some sources are unclear, but there is a strong possibility that “the Lord’s day” is a reference to the Jewish Sabbath. (Even the only New Testament use of that phrase in the Revelation to John may mean Saturday rather than Sunday.) Yet from the rest of this writing it is clear that it means Sunday.
Some of the practices of this document have fallen by the wayside. These would include, in some places, a formula prayer during and after the Lord’s Supper. They would necessarily include the need to determine a true prophet from a false one, since the gift of prophecy ended soon after this document was written. They would also include fasting, and requiring one being baptized to fast.
It continues to be an interesting document, and a brief guide to life. Whether one could require every detail of it is questionable.