If I take that question as serious it would call in to question on you being Roman Catholic since the RCC holds that the OT and NT is inspired Scripture. These questions are those of one who rejects Christianity altogether or that of atheist or agnostic. Casting doubt in God’s Word is the lie of Satan . Always remember that. Your question very much reminds of me the serpent in Gen 3 who deceived Eve in to eating the forbiding fruit by causing doubt of God’s Word. Thats not a good thing.
For Catholic (and Orthodox and Oriental and Assyrian) we have no problem with affirming the Scripture as Word of God, because we resolve to two sources: The Apostolic Succession and the Tradition.
But from Sola Scriptura reasoning, those Tradition and authority of Apostolic Succession are profitable, and since it cannot be directly asserted in the Scripture, is fallible.
This creates a problem: When the Scripture is not yet canonized, you need authority that work within sola scriptura method to doctrinally assert that this book and not that one, is part of Scripture. But you not have yet a bundle of books called Scripture with Old and New testament.
Thus logically speaking, the book you now regard as Scripture, is a fallible collection of infallible books.
The probability that the books inside that collection are actually not Word of God will always be there.
Thus the question regarding canon:
Does the canon can be considered doctrine? By the canon it means that these and only these books are to be regarded as scripture, infallible word of God, distinct from different books even if they are most profitable.
And, the question that public revelation is definitely closed, isn’t it part of doctrine? Is it important for salvation to affirm this?
But is this definite teaching that public revelation ended with the last apostle contained in the scripture? Why draw the line with the last apostle?
If it not important for our salvation, then the question that further revelation in par with the
current scripture is impossible to reject.
Like other poster said, confessions, traditions, catechisms, are profitable but not infallible.
These two questions, I believe, is more than profitable, it is very important. Are these mere fallible but profitable tradition, or something we can give assent of faith?
If these two questions are only fallible-although profitable tradition, we cannot rule out new revelation, such as the additional Mormon scripture.