Before reading others’ answers:
A. 5D. Not sure exactly what the 4NT bid is supposed to mean, but presumably if he’s asking for Aces, he has a heart fit and slam aspirations despite knowing I have <10 HCP? In which case, we would likely set 5C, but should surely make 5H. But then he passed 5C, so I assume he is on the low end of his conveyed strength. I bid 5D to show him a feature and a potential trick. He knows I don’t have the Ace, presumably he thinks I have Kxx or QJx. He can convert to 5H, 6H or leave as 5D if he has strong diamonds. I also considered double or pass. With them vulnerable maybe we are more profitable setting 5C by a number of tricks. But I would think partner would have doubled the 5C bid.
B. 2NT. It’s aggressive. My club “stopper” is weak and it’s a risk. Again. Not positive what his 2D rebid means. Opposite no overcalls, I would assume 11-15 points, 5+D. With the overcall in there, it is less clear to me. I considered Pass (2D best chance), 3D to show diamond support and some strength. I’m assuming my 2NT shows decent strength in my range and stoppers in C, H, S, taking a chance for 3NT, he can convert to 3D if he prefers.
C. 2H. I think 2C is just a touch too strong. 2H tells partner I have 5 hearts, and not just 4, and enough to rebid.
D. Double. Maybe I’m not supposed to double with 2H, but it feels like it describes my hand the best. Outside of spades we have lots of options, and I have 12+ points, so I like that it is open ended on the top end. Presumably 2H is the other primary contender? Seems like both are strong? But are we two strong for 2H?
E. 5C. I strongly considered 4NT, but with clubs as trump, we may be in trouble if he’s missing the Ah, Kh, Kc/Qc. I considered 3D, but good chance partner passes.
F. 1S. This seems strong enough to open in 3rd seat. And 1D gives us rebidding problems to show spades. And if we’re going to open diamonds, it could have been 2D. Let’s show our nice major suit and we can rebid diamonds.
G. 2H. Seems straightforward to me. What am I missing here? Something creative?
H. AC. Maybe I’m too straight forward here, but we need 3 tricks, obviously want to maximize beyond that, but there is some risk we can’t get our 3. And I fear that we have a situation where there are extreme distributions with N-S holding a majority of clubs and hearts, clearly E-W is short in those suits and holds a majority of spades and diamonds. So I fear that they will be able to pull trump and then dump a singleton or even doubleton losers in hearts or clubs on diamond tricks. I considered the 5 of diamonds to short suit myself, but I don’t want to give control to E-W immediately. So I probably start with Ac, and then follow with 5d.