What is the ruling regarding a prayer intentionally abandoned in childhood due to laziness, and is it obligatory to make it up if it is unknown whether the abandonment was before or after puberty, or if it occurred once or repeatedly?

Neglecting prayer is a major sin, and according to some scholars, it can even amount to disbelief.

If the questioner has indeed prayed, there is no make-up prayer (qada') due upon her. However, if she doubts whether she missed a prayer, she must make up whatever she is not certain she performed, because the prayer is a certainty owed (in one's responsibility), and this obligation is not discharged except with certainty. Nevertheless, Hanafis hold that make-up prayer is not obligatory if the doubt arises after the time for the prayer has elapsed; strong presumption suffices.

If the doubt concerns reaching puberty at the time of neglecting the prayer, then make-up prayer is not obligatory because certainty is not removed by doubt, and the default is not having reached puberty until the contrary is confirmed.