Question: Should one comfort a mourner when he enters shul on Friday night?

 Short Answer: There is a custom for the minyan to comfort the mourner when he arrives in shul before the onset of Shabbos on Friday night. Some even allow such comforting on Shabbos itself.

Question: May an aveil who is sitting shiv’ah in the house of the deceased (or of another aveil) return to his own home at night to sleep? May he attend shul if there is no minyan at the beis aveil?

Question: May an aveil attend his regular Daf Yomi shiur on Shabbos during shiv’ah? 

Short Answer: While the Aruch HaShulchan appears to allow an aveil to attend his regular shiurim on Shabbos, the minhag, as cited by many contemporary poskim, is that an aveil does not attend any shiurim on Shabbos during shiv’ah.