Answered by Shaykh Sohail Hanif, SunniPath Academy Teacher
In salah if you recite a surah that comes earlier in the quran in the second raka, do you have to do sahu?
Reversing the order of the suras is prohibitively disliked only if done intentionally (f: and aware of the ruling), as mentioned by Ibn Abidinin his Hashiya.
Even then, however, although one has sinned (f: if intentional), one isn’t expected to offer a prostration of forgetfulness because observing the order of the suras is of the necessary elements of reciting the Qur’an not of the prayer itself as mentioned in Bahr al-Ra’iq of Ibn Nujaym.
And Allah knows best.
Sohail Hanif [& checked by Faraz Rabbani ]