Both questions are irrelevant. By sticking with Sola Scriptura we are on firm footing. How many times in the Bible does it say not to add to or take away from what is written? Or if anyone, even an angel of light, were to to bring any other gospel, other than what we have preached, let him be accursed? Do any of those warnings mean anything to you?
They are relevant since you (Pl) embrace denominations, sects, and cults that deny the Holy Trinity. Those associated with those groups hide their affiliations and refuse to truthfully and transparently answer that simple question. They knock on your door at home and seek to prosthetist you on the RF.
By sticking with Sola Scriptura we are on firm footing.
False; neither the Messiah nor the apostles gave that doctrine; it came along almost fifteen centuries later. Many of the cults devolved from the Protestant reformation of the Christian faith also hold Sola Scriptura. The doctrine, like OSAS, is not the insurance policy you seem to think it is.
How many times in the Bible does it say not to add to or take away from what is written?
It is written about the law of Moses, in both the Torah and in Matthew. Doesyour faith community add to or take away from the law of Moses ? It is written in the book of Revelation, the book where the Messiah is looking for "works." Does your faith community emphasize works ? It is not written in the Bible with respect to what constitutes the Bible. It was left to the successors of the Apostles to decide which books were in the Bible.