[Knurdler]

These questions are on only the forcing sequence: 1m 1M 1NT 2D.
I am comfortable to use the rule that opener chooses lowest available bid. ie 2H before 2S.

I have read that if opener rebids 2H, responder can ask if opener also has spades by bidding 2S. However, I have also read that if opener rebids 2H and responder then bids 2NT, this is also asking about spades (otherwise why use TWCB?).

Question 1: after 1m 1H 1NT 2D 2H how does responder choose to rebid 2S or 2NT?
Perhaps the 2S rebid confirms a 53 heart fit and is looking for a 44 spade fit, whereas the 2NT rebid denies a 53 heart fit and is looking for a 44 spade fit? Perhaps it is to do with who declares in spades?

Question 2: after 1m 1S 1NT 2D 2H how does responder choose to rebid 2S or 2NT? Responder would not look for a 53 spade fit unless there was no 44 heart fit. Perhaps 2S shows 6 spades and 2NT shows 5?

[DavidKok]

Question 1: on 1m-1♥; 1NT-2♦*; 2♥ I play the simple:

• 2♠: 44M, no heart fit, looking for a 4-4 spade fit.
  
• 2NT: 4H, not four spades, no five card minor, wants to investigate a possible (minor suit or NT) slam or perhaps keep the possibility of playing in the Moysian live.
  
• 3m: 5H, 4m. Weird, but symmetric with opener responding 2♠ or 2NT instead.
  
• 3♥: Confirms hearts, slammish.

Higher bids should be splinters setting hearts, with 3NT not existing (we haven't learned anything important new since last round so why bid 3NT now rather than over 1NT).
One feature that I think is important is that while there is overlap in the responses over all these bids, opener has no idea about the degree of fit so far. If you wish to have a good dialogue auction to slam it pays to confirm the existence of an 8 card trump fit as soon as possible, so responder has to show this immediately.

Question 2: similar to the above, I'd rebid 2♠ with 5(+) and 2NT with four spades and interest in a contract other than 3NT. Theoretically 3m should again be 5♠4m, but I don't recall this coming up. Keep in mind that 1m-1♠; 1NT-3♠ is a slam try with 6(+) spades and sets trumps (with an invitational hand with 6(+) spades bid 2♣ first), so most of the hands going through 2♦ are not that hand type. I also have different routes for showing a 55 and a 64, so those hand types are ruled out, and 5m4M GF starts with the minor suit.