#1 (easy)
You might bid 2NT (upgrading to 18) not 3D, sure. Anyway, opps lead the H2 (4th best). You duck in hand hoping they'll continue hearts but no such luck: East switches to the D3 to the ten and king, and West continues another heart.
#2 (medium)
OK, you may not want to reward partner for her aggressive raise to 3H, but all's well that ends well. Can it end well though? West leads DQ (standard leads), East playing the 3 (encouraging). If you duck West continues with DJ.
#3 (hard)
Perhaps North might have picked 1NT, but instead landed you in this ghastly contract with mirrored pancakes (maple syrup optional). West leads the S8 (3rd/5th). If you cover with the T then East will play Q, otherwise 6. If you draw trumps then West has Qx.
ahydra