How do we pause on (tar) in His saying (the Most High), "Have you not seen (alam tar)": with a sukoon or a fatḥa, and is it permissible to add tanween to the disconnected letters at the beginning of the surahs?

Stopping at (ألم تر) should be with sukoon (quiescence) and not with fat-h (vocalization), and this is for necessity or for testing. The nunation (adding tanween) to the disconnected letters (al-Huroof al-Muqatta'ah) at the beginning of the surahs is not permissible, neither in pronunciation nor in writing, because it is a distortion. Indeed, they were revealed and transmitted without nunation, and the majority of scholars agreed on the obligation of following the Uthmanic script of the Mushaf.