Different standards that exclude the possibility of other divinely inspired canons. They can't all be right but they CAN all be wrong.
Possibly, but as I said, Prophetic and Apostolic authorship should be the number one priority.
But sadly, it isn't.
With a few exceptions, nearly all of what we consider "Christian" groups, accept our current "canon".
The Old Testament canon closed some 400 years prior to the birth of the Lord. Now, there is a cry to re-open the canon and include more non-canonical books such as "Enoch". Which is accepted by the Ethiopian Church.
And even more recently, there has been an outcry to re-open the New Testament canon to include the Gospel of Judas.
I am one of those types that, unlike others, I have read most of the Apocrypha, Pseudepigrapha books just purely for information's sake.
Now, here is what I know as far as "canonicity" is concerned:
1. Written by a recognized prophet or apostle.
2. Written by those associated with recognized prophet or apostle.
3. Truthfulness (Deut. 18:20-22).
4. Faithfulness to previously accepted canonical writings.
5. Confirmed by Christ, prophet, apostle (e.g. Luke 24:44; 2 Pet. 3:16).
6. Church Usage and Recognition. (While adopted, although not widely used, with the exception of the OT Apocrypha books, nearly the entire standard for Christianity was adopted at The Council of Carthage, circa AD 397)
And like I said, although adopted, some "Christian" churches like the Ethiopian Church, have their own "canon". The standard Christian canon is 66 books. The Ethiopian Church includes 81 books.
And here again, some groups who call themselves "Christian" have their own canon. One that springs to mind right off the bat are The Church of Jesus Christ of Latter Day Saints. The Mormons who use the book of Moroni.
I can't speak as to why some have a larger canon than others, why this group accepts one canon over the other. But I can say this, the 66 books we know of that we call our "Holy Bible" passed all the test for canonicity.
And that is good enough for me.
God Bless
Till all are one.