An insufficient 3NT bid
Yesterday I had a case. Dealer bid 1H, LHO bid a preemptive 4C, and then Responder bid an insufficient 3NT. Opp din't accept it, and Responder bid 4NT. According to law 27B1(a) this is allowed, and I think 27D is waiting... Is Opener entitled to pass, or he should reply, for example aces? And if he passes, does 27D take action? And what is your decision if 4NT just makes.
B scenario hypothetically, LHO made a 4S preemptive bid this time, and Responder bid the same insufficient 3NT. What about 4NT bid, which now is more complicated as it could be: to play, asking aces, or the minors. Is there any difference with the previous real case?