Question:

In the flyer this was also written that, recite subhaanallah (سبحان الله) three times in the third and fourth rakat of the fardh prayer instead of surah Fatihah. Yes in all three rakats of witr it is necessary to recite Fatihah and a surah.

Similarly in the last sitting one may simply recite اللهم صل على محمد واله instead of the complete durood and the masnoon dua.

My question is that, by doing the above will the qadhaa be fulfilled?

Answer: حامدا ومصليا ومسلما

Yes it will be fulfilled. It will be sufficient to recite subhaanallah (سبحان الله) three times in the third and fourth rakat of the fardh prayer. However, it will be necessary to recite a surah along with Fatihah in the third rakat of Witr.

The person upon whom there are many qadhaas remaining, he may suffice on a short durood in place of the duroode Ibrahim in the last sitting, to facilitate the ease of making up his prayers as is mentioned in the question.

Similarly there will also be leeway for him to leave out the dua that is usually recited after the durood in the last sitting.

And Allah ta’aalaa knows best.

Hazrat Mufti Ahmad Khanpuri Saheb (May Allah preserve him)
Mahmoodul Fataawaa 1/468-469