What is the end time for fajr mustahab namaz and other than namaz e shab, is it permissible to perform qadha for the daily nafilah?

(Nafilat alfajr) fajr mustahab prayer ends a little bit before sunrise when a redness is visible in the sky.
It is permissible and recommended to do qadha for daily mustahab prayers if we couldn't pray them on time.