If a man delays a prayer until just before the next prayer, and he catches the opening takbir before the second prayer begins, he has caught the time

The Shaykh : If a man delays a prayer until just before the next prayer, and he catches the opening takbir before the second prayer begins, he has caught the prayer in its time, except for the Fajr and 'Asr prayers. For these two prayers, one must catch the first rak'ah of each before their times end in order to be considered to have caught them. So, if a person is praying Fajr and says Allahu Akbar, and the sun rises, his prayer is invalid. However, if he has already raised his head from the first prostration when the sun rises, he continues his prayer and his prayer is valid. Likewise, the person praying 'Asr: if he says Allahu Akbar and the sun sets, his prayer is invalid. Although this scenario is rare to imagine, if he prays one rak'ah before the sun sets... regarding the 'Asr prayer, catching the time in these two prayers, Fajr and 'Asr, is by catching the first prostration of the first rak'ah. As for the remaining five prayers, catching the time is by catching the first takbir before the time of the next prayer begins. This is regarding catching the time and the validity or invalidity of the prayer.
As for delaying the prayer, it is permissible for a Muslim to delay the prayer until just before the next prayer, even without a legal excuse, provided that he does not miss the congregation, for example, if there is a congregation. Except for the 'Asr prayer, it is not permissible for him to delay it until the sun turns yellow; that is, about a third of an hour, or roughly half an hour, before sunset. It is not permissible to pray the 'Asr prayer, even if he catches it in its entirety, ten minutes before the sun sets, because he would be praying it in the time of dislike. The Messenger (peace and blessings be upon him) named it the prayer of the hypocrite.