1) I would use 2!D as GF xzy if available, if not, 2D as nmf. If partner shows heart over xyz, I will bid 3H setting trumps and as a slam try (I have 36 Zar points and partner should have at least 26 putting us in slam range. I need a
♦ control from partner to try for slam. I would hate to get to high if he had KQx QJx JTx Axxx for instance. Once partner shows a minimum hand with only
♥, I would apply the brakes, as regardless of the zar point total, misfits have to be devaluated. I would consider both 3NT and 4
♥, my scattered values and those nines suggest 3NT, especially if partner a) could have 4
♠ and

could have one heart (probably can't have both however)./
2) They have stretched to game and declearer has bid three suits, must be short in clubs. I would lead a spade now, and depending upon what we discover, everytime I get in.
3) Ugly hand. The two strategies (other than if you play at these colors (1s)-3H as an intermediate hand) are dble first then bid hearts and bid hearts first and then double. There are problems with both. With a spade void if you double first, you may not get a chance to show your hearts. Likewise with a spade void, if you bid hearts first, you maybe put into the awkward position of considering a reopening double with a void in their suit... this is something I am lothe to do without a lot of reasonably sure tricks in my hand.
So I will bid 2
♥ initially, as I may never get a chance to show my suit if I don't bid it now. Over game try three spades, I guess I will reluctantly have to pass. I have 16 hcp, RHO had an opener and LHO had an invitational raise, my 16 and their expected 20 to 24 hcp leave partner with from 0 to 4 hcp, and they are probably on the upper end of that range. So that two bad things can happen if I double. First, partner might bid 4 of some suit and we get doubled and go down a few, second, partner who is probalby has 3 or 4 spades might pass hoping for the best with his weak hand (and expecting me to have a spade). We might beat 3S one, or it might make. But at imps I am willing to accept my +50 to avoid doubling them into game. If 3S was preemptive raise, I would double at my second oppotunity.
4) Four heart bidder has a big hand but didn't open 2NT. So the assumption is he is distibutional with a source of tricks (diamonds) and strong. Hopeing to set up quick tricks in spades seems to be a pipe dream, but I do have the club queen, so I hope to hit a useful club combination in partner hand and would guess to lead a club.