Posted 2024-September-30, 10:49
#1: A very popular agreement is to play system on after a 1NT overcall. Another very popular agreement is to play system on after a 1NT opening and 2♣ overcall. Taken together, I would expect the most common meaning here to be 5+ hearts, particularly amongst ADV+ players. A final thought is that a third popular agreement is to play that in 2-suited auctions, bidding RHO's suit is natural while bidding LHO's suit is artificial. So if the answer is not hearts then it is quite likely to be both majors. Either way, the 1NT bidder should probably just bid 2♥ now and wait to see what happens next.
#2: By the same logic as in #1, the most common meaning for this is Stayman, followed by takeout. Unless you are playing with someone who learned to bid under Culbertson, in which case it is clearly penalty. Aside from that one exception, Overcaller should just bid a 4 card major now without worrying too much about anything else.
#3: Yes, when the call over 1NT is 2♦ rather than 2♣, this makes a significant difference, since you can no longer play an easy system on scheme. In this case, the default amongst good players is TOX + natural + Lebensohl, while the default amongst club players tends to be Stolen Bid with the cue replacing GF Stayman. Weigh up your partner (and what your partner thinks of you) and then take the action that seems to present the least risk.
(-: Zel :-)