Question: Is it a prohibition of yichud for a boy and girl to go hiking in a state park on a shidduch date?

 Short Answer: Assuming that the park is frequented by other visitors who will be able to see the shidduch daters every few minutes, it is permitted. There is further discussion, however, in the poskim whether the shidduch daters violate yichud when going in a car together on secluded roads.

Question: May a person act leniently when faced with a situation that is possibly, but not certainly, yichud? 

Short Answer: There are many poskim, including Rav Moshe Feinstein zt”l, who appear to allow one to act leniently when faced with a situation that is possibly, but not certainly yichud d’Rabbanan (Rabbinic).

Question: Is there a prohibition of yichud when two frum men are secluded with one frum woman?

 Short Answer: Assuming that both men are upright men, there is no problem for two Ashkenazi men to have yichud with a woman in a city during the day. The exact definition of “upright,” though, is subject to dispute.

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.