Answers: (Material in blue is more advanced.)
The purpose of this set of problems is to instill a habit of planning ahead. If you make what you consider the "normal" bid, you may have problems on your next bid - whereas if you foresee the problem, you can avoid it by choosing a different call.
1.
Hint: How will you handle a spade bid by partner?
Answer: You might consider passing. However, bidding hearts has the effect of getting a desired heart lead, and perhaps making their bidding more difficult, especially if partner gets active. However, it is
your side's bidding that will be more difficult if you open 1H and partner responds the expected 1S. If you bid again, partner will think you have an opening hand - some partnerships say you should have a chance at game opposite a passed hand. Also, 1H-1S-2D could have 18 points, and partner may get too high catering to that hand, and a 1NT rebid encourages partner to rebid a 5-card spade suit. Even a 2H rebid (showing 6) could have as much as a bad 16 points so partner may invite.
Once you see the problem, you can avoid it. Rather than opening 1H, open 2H (weak.) You steal a lot of room, and get your desired heart lead.
It is fairly commonplace for a third seat weak two bid to have only five cards, so partner shouldn't take you too high trying to further the preempt.
The recommended opening bid is 2H. The 2H opening bid pays off big when partner has a weak hand with five spades and would have led a spade against notrump without your bid.
2. You are the dealer. Your call?
Hint: How will you handle a spade bid by partner?
Answer: If you open 1H and partner responds 1S as expected, you have no good call. You have about 16 counting your heart length. 1NT, showing 12-14 is a significant underbid. 2NT showing 18-19 is a significant overbid. 2H showing hearts shows a minimum hand and six hearts while 3H shows six or more good hearts. 2 of a minor would show an unbalanced hand and partner could easily pass leaving you in a 3-3 fit.
The problem is that you have a balanced hand in the range of your opening 1NT bid. The way to show that hand is to open 1NT. Yes, it is true that occasionally you will miss a 5-3 heart fit. Frequently those hands will play as well in 3NT, but occasionally you'll get to show the five hearts (for example, 1NT-2C Stayman-2H (shows 4) - 2NT (invite; my 4-card major was spades) - 3H (I'm accepting and showing a fifth heart.) The upside for opening 1NT is that you shouldn't have an awkward hand to bid.
There have been several times I've opened 1NT on this type of hand and ended up getting a heart lead against notrump - another bonus for opening notrump instead of hearts.
The recommended opening bid is 1NT.
3. You are the dealer. Your call?
Hint: How will you handle a spade bid by partner after West bids hearts?
Answer: This one was harder to foresee; you think you can handle a 1H response or a 1S response by rebidding 1NT. This doesn't work out so well when the opponents bid hearts, and partner will expect you to have hearts stopped when he raises your 1NT rebid to game.
If you opened 1C, you now have no good call over partner's forcing 1S bid. You must bid as partner could be quite strong; 2C on a 4-card suit is awful; 2D is a reverse (a bid that forces your partner to go back to the three level if he likes your first suit better), and should show at least a medium opening hand; raising spades on a doubleton isn't likely to work, nor is bidding 1NT with three small cards in the opponents' suit.
However, if you opened 1D, you have an easy 2C bid now. 2C is no longer a reverse since your partner, with a minimum hand and liking diamonds better, can go back to your first suit at the two level.
The recommended opening bid is 1D.
4.
Hint: How will you handle a spade bid by partner?
Answer: Your partner's 1S response, while not his most likely response, is within the scope of responses that you should have prepared a rebid over.
Since partner's spade bid could be made on four small spades, any spade raise is out of the question; indeed any jump in spades by you guarantees four-card support.
Nor does any diamond bid work. A jump to 3D shows 16-18 points; you have 21 if you count length
(personally I would add 1 point for the diamond length because it might be valuable but the suit isn't that good - giving me 20.) If you don't belong in spades, you might belong in 3NT and any diamond jump higher than 3 not only bypasses 3NT, your likely final contract, but also overstates the diamond suit.
What about notrump? A jump to 2NT shows 18-19; I believe this hand is stronger than that. A jump to 3NT will shut out a spade fit if one exists.
You don't have a balanced hand, However, you probably want to play in notrump unless partner has five spades (which he can show over any notrump opening bid) or six hearts that weren't good enough to open a weak 2 bid. You have the approximate strength for a 2NT opening bid, and rather that deal with the rebid problem that comes over 1D-1S, I recommend that you open this hand 2NT.