What are the signs of puberty that affect the onset of accountability for actions, and will one be held accountable for immoral acts committed before puberty?

A person is not held accountable for religious transgressions before reaching puberty, as the Prophet (peace be upon him) said: "The pen has been lifted from three: from the insane person until he recovers, from the sleeper until he wakes up, and from the child until he reaches puberty." However, after puberty, transgressions are recorded against him. Nevertheless, Allah Almighty guarantees to expiate minor sins for those who avoid major sins, as He states: "If you avoid the major sins which you are forbidden, We will remove from you your lesser evil deeds and admit you to a noble entrance." And "the one who repents from sin is like one who has no sin," as stated in the Hadith. Allah Almighty also said: "And indeed, I am the All-Forgiving to whoever repents and believes and does righteousness and then is guided," and "Say, 'O My servants who have transgressed against themselves [by sinning], do not despair of the mercy of Allah. Indeed, Allah forgives all sins. Indeed, it is He who is the Forgiving, the Merciful.'" The solution lies in sincere repentance from all sins, through remorse and a firm resolve not to return to them.