Does a person reach full maturity at the age of forty and is not held accountable for his deeds before this age?

"Reaching full strength" (بلوغ الأشد) signifies the completion of youthful vigor and intellect. It begins from puberty until the age of forty, as mentioned by Al-Baghawi. Scholars have differed in defining "reaching full strength": some say it is nocturnal emission, others say reaching eighteen years of age, and still others say reaching forty. Accountability for a person's deeds begins from puberty, as stated in the Hadith: "The pen is lifted from three: from the sleeper until he awakens, from the child until he reaches puberty, and from the insane until he regains sanity." Another Hadith states that no sin is recorded against a newborn until he reaches the age of accountability. And if a Muslim reaches the age of forty in Islam, Allah grants him immunity from madness, leprosy, and vitiligo.