You mean pray for damned who committed mortal sin. When did that practice begin?
38 Then Judas assembled his army and went to the city of Adullam. As the seventh day was coming on, they purified themselves according to the custom, and they kept the Sabbath there.
39 On the next day, as by that time it had become necessary, Judas and his men went to take up the bodies of the fallen and to bring them back to lie with their kinsmen in the sepulchers of their fathers. 40 Then under the tunic of every one of the dead they found sacred tokens of the idols of Jamnia, which the law forbids the Jews to wear. And it became clear to all that this was why these men had fallen. 41 So they all blessed the ways of the Lord, the righteous Judge, who reveals the things that are hidden; 42 and they turned to prayer, imploring that the sin that had been committed might be wholly blotted out. And the noble Judas exhorted the people to keep themselves free from sin, for they had seen with their own eyes what had happened because of the sin of those who had fallen. 43 He also took up a collection, man by man, to the amount of 2,000 drachmas of silver and sent it to Jerusalem to provide for a sin offering. In doing this he acted very well and honorably, taking account of the resurrection. 44 For if he were not expecting that those who had fallen would rise again, it would have been superfluous and foolish to pray for the dead.
Engelbrecht, E. A. (Ed.). (2012). The Apocrypha: The Lutheran Edition: Text (2 Mac 12:38–44). Saint Louis, MO: Concordia Publishing House.
The Longer canon as you put it actually teaches that it is actually not part of the canon at all!
37 So I took the five men, as he commanded me, and we proceeded to the field and remained there. 38 And on the next day, behold, a voice called me, saying, “Ezra, open your mouth and drink what I give you to drink.” 39 Then I opened my mouth, and behold, a full cup was offered to me; it was full of something like water, but its color was like fire. 40 And I took it and drank; and when I had drunk it, my heart poured forth understanding, and wisdom increased in my breast, and 5 my spirit retained its memory; 41 and my mouth was opened and was no longer closed. 42 And the Most High gave understanding to the five men, and by turns they wrote what was dictated, in characters that they did not know. They sat forty days and wrote during the daytime and ate their bread at night. 43 As for me, I spoke in the daytime and was not silent at night. 44 So during the forty days ninety-four 7 books were written. 45 And when the forty days were ended, the Most High spoke to me, saying, “Make public the twenty-four books that you wrote first, and let the worthy and the unworthy read them; 46 but keep the seventy that were written last, in order to give them to the wise among your people. 47 For in them is the spring of understanding, the fountain of wisdom, and the river of knowledge.” 48 And I did so.
Engelbrecht, E. A. (Ed.). (2012). The Apocrypha: The Lutheran Edition: Text (2 Esd 14:37–48). Saint Louis, MO: Concordia Publishing House.
There's the traditional 24 books of the Tanakh. The number will vary between 22 and 24 depending if the collection puts Ruth with Judges and Lamentations with Jeremiah. Flavius Josephus makes the same point in Against Apion:
"For we have not an innumerable multitude of books among us, disagreeing from and contradicting one another [as the Greeks have], but only twenty-two books, which contain the records of all the past times; which are justly believed to be divine; (39) and of them five belong to Moses, which contain his laws and the traditions of the origin of mankind till his death. This interval of time was little short of three thousand years; (40) but as to the time from the death of Moses till the reign of Artaxerxes, king of Persia, who reigned after Xerxes, the prophets, who were after Moses, wrote down what was done in their times in thirteen books. The remaining four books contain hymns to God, and precepts for the conduct of human life. (41) It is true, our history hath been written since Artaxerxes very particularly, but hath not been esteemed of the like authority with the former by our forefathers, because there hath not been an exact succession of prophets since that time . . . "
Josephus, F., & Whiston, W. (1987). The works of Josephus: complete and unabridged (p. 776). Peabody: Hendrickson.
So what good is the Longer Canon? Perhaps providing a way to ward of demons and cure cataracts.
2 Now as they proceeded on their way they came at evening to the Tigris river and camped there. 3 Then the young man went down to wash himself. A fish leaped up from the river and would have swallowed the young man; 4 and the angel said to him, “Catch the fish.” So the young man seized the fish and threw it up on the land. 5 Then the angel said to him, “Cut open the fish and take the heart and liver and gall and put them away safely.” 6 So the young man did as the angel told him; and they roasted and ate the fish.
And they both continued on their way until they came near to Ecbatana. 7 Then the young man said to the angel, “Brother Azarias, of what use is the liver and heart and gall of the fish?” 8 He replied, “As for the heart and the liver, if a demon or evil spirit gives trouble to anyone, you make a smoke from these before the man or woman, and that person will never be troubled again. 9 And as for the gall, anoint with it a man who has white films in his eyes, and he will be cured.”
Engelbrecht, E. A. (Ed.). (2012). The Apocrypha: The Lutheran Edition: Text (Tob 6:2–9). Saint Louis, MO: Concordia Publishing House.