while replying to "Ashadu Anna Muhammed ar Rasoolullah" are we supposed to say (sallahu alahai wasallam) ...one mufti here calls it makroof..one calls it bidah and third calls it mustahabb

1. According to the narrators of Hadith, we are supposed to repeat the exact words of the Muazzin except for 'Hayya alas Salaah' and 'Hayya alal Falaah'. There is no mention of saying the words, 'Sallallaahu Alayhi Wasallam'. However, if one does so, without thinking it to be necessary, then we do not see any harm in it.
2. This Hadith is recorded by Imaam Abu Dawud in his Sunah, Hadith529. The chain of narrators have been classified as weak. (Mukhtasar al-Munzhiri vol.1 pg.285). However, such a Hadith can be used to establish Istihbaab? The fact that it is weak does not necessitate its total rejection.

and Allah Ta'ala Knows Best

Moulana Muhammad ibn Moulana Haroon Abbassommar
FACULTY OF SPECIALTY IN HADITH

CHECKED AND APPROVED: Mufti Ebrahim Desai