77:18 If there are not two loaves for each diner, rather only one set before one person, then he can fulfill the obligation of two loaves for everyone with his bracha. Similarly, one person can recite bentching for others (even if they know how to bentch – Bi’ur Halacha 167:11 s.v. echad mevareich). Before reciting the bracha, he should say, “B’rshus…” (“with your permission…”). After the one who made the bracha eats from one of the loaves, he distributes a piece to the other diners and they eat. (The bread should be placed in front of the diners but not directly in their hands - OC 167:18).
77:19 If one did not review the weekly Torah portion on Friday, he should not eat on Shabbos morning before doing so. (This is not, however, a reason to delay the meal until after midday - Mishnah Brurah 285:9.) If he ate before reviewing it, he should make sure to do so before the Mincha. After the fact, the parsha may be reviewed until Tuesday night.