What if prayer is repeatedly delayed beyond its time due to sleep or forgetfulness; is there sin upon the one who did not intentionally delay it? And what are the means that help in performing prayer on time?

You must strive to perform the prayer on time. If you miss it without negligence, such as sleeping before or after its time while having taken measures to wake up, then there is no sin upon you, even if this recurs. This is based on the Prophet's (peace be upon him) saying: "There is no negligence in sleep. Negligence is only on him who does not pray a prayer until the time of the next prayer comes. So, whoever does that, let him pray it when he remembers it." And his saying: "Whoever forgets a prayer or sleeps through it, its expiation is to pray it when he remembers it."