The failed "Big Cutover" of the early church

Francis, you acknowledged in your opening statement that oral tradition was necessary and taught by the apostles before scripture was "completed and circulated". Especially given that some books of the NT are not written by apostles, it's not clear to me how anyone would know when scripture is completed. And since I presume part of the criteria for knowing scripture is complete is at least death of the apostles, and since sola scriptura is apparently not in effect when the apostles are alive, we presumably have a situation where sola scriptura can't be an apostolic teaching, since it doesn't work when the apostles are alive. Having acknowledged that the earliest church never practiced sola scriptura... (a) who gave the order for the church to change from tradition to sola scriptura? (b) where did they get the authority to do so? (c) Why do the Apostolic Fathers never mention the Big Cutover? (d) where can we find evidence the order was given? (e) why did the early church never end up cutting over to the new regime? (f) Whose fault was it the early church "forgot" to change to sola scriptura? (g) What year should the cutover have happened, and how would it have proceeded if it hadn't failed?