Q 1: It is related in the Authentic Hadith
When night falls or it is evening, do not let your children out...
Until his statement,
... Turn off your lamps
Is this command obligatory or desirable? If it is an encouragement, what makes it to be understood as such and not as a command?
The commands mentioned in the Hadith only indicate desirability according to the majority of scholars as stated by some scholars including
Ibn Muflih in his book (Al-Furu`, Vol.1, p. 132) and
Al-Hafizh ibn Hajar in (Fath-ul-Bary, Vol. 11, p. 87). Finally, Allah knows best.May Allah grant us success and peace and blessings be upon our Prophet Muhammad, his family, and Companions.