On both Boards 3 and 4 there was the possibility of making
13 tricks in NoTrumps. Can you bid 7NT ? I think neither
is a good contract.
Board 3 I would open 1C as West, East bids 1S, and now I
would stretch a bit and rebid 3C as West, showing 16+ points
and a 6-card suit, which is the key to making 13 tricks.
Hearing this East can take control and ask for aces and then
kings. Finding them all present I still think end in 7C
which is a safer contract than 7NT.
only has 6 points and they are actually pretty poor, so do
not respond 2H but simply a negative 2D, which will slow
East down. 3C rebid from East, now 3H from West, and then
3S from East finally finds the spade fit. I think West
could still just sign off in 4S now. East has all the
aces, and only two losers for West to cover, but needs a
king from West, and not a 4-1 trump break.
4NT then 5NT would reveal that West has no kings, but now
you are at the 6-level anyway, so might just have to play in
6S. Yes, 7 makes because there is no diamond loser and the
heart king can be picked up, but it's not a great contract.