Is it permissible to intentionally or unintentionally delay the Sunnah prayers past their prescribed time, such as praying the Sunnah of Maghrib after Isha? And is it permissible to intend to pray Duha twelve rakahs along with the Sunnah prayers of the obligatory prayers, or to intend to pray Duha and Tarawih together?

One should pay attention to the regular Sunnah prayers (Sunan al-Rawatib), and it is desirable to make them up if they are missed due to forgetfulness or being preoccupied. It is not permissible to combine the Duha prayer and a regular Sunnah prayer with a single intention, because each of them is intended for its own sake. Acts of worship that are intended for their own sake do not overlap, unlike those whose intention is merely the act itself. Thus, the Duha prayer cannot be combined with making up Witr or the night prayer (Qiyam al-Layl) with a single intention. If Witr is missed during the day, it should be made up as an even number of rak'ahs.