How many distinct tragedies does the Rambam list as having occurred on the Ninth of Av?
Halacha 3 (idx 2) explicitly enumerates five tragedies on Tisha B'Av: the decree against the desert generation, the destruction of the First Temple, the destruction of the Second Temple, the fall of Beitar, and the plowing of Jerusalem.
Question 2
Which women, normally exempt from the other commemorative fasts, must nevertheless complete the Tisha B'Av fast in full?
Halacha 10 (idx 9) states that pregnant women and those who are nursing, although absolved from fasting on the other commemorative fasts, must complete their fasts on Tisha B'Av.
Question 3
What specific marking must be left on the walls of one's home as a permanent reminder of the Temple's destruction, according to the post-Temple Sages' ordinance?
Halacha 12 (idx 11) rules that one must leave a space one cubit square opposite the doorway undecorated, even though the rest of the walls may be covered with mortar and lime.
Question 4
Under what condition is a person who travels frequently to Jerusalem NOT required to rend his garments upon arriving?
Halacha 18 (idx 17) states that if a frequent visitor comes to Jerusalem within thirty days of his last visit, he is not required to rend his garments; if more than thirty days have passed, he must rend them.
Question 5
What is the ultimate fate of all the commemorative fasts in the Messianic era, according to the final halacha of this chapter?
Halacha 19 (idx 18) teaches that all these commemorative fasts will be nullified in the Messianic era, transformed from days of mourning into days of joy and festivity, since the redemption renders the original causes for mourning obsolete.