LEARNING CENTER

2. You have no interest in game (I hope), but you should try to improve the contract. This bid is sometimes called "garbage Stayman". The great thing about it is that you don't need an agreement. Your partner will respond either 2, 2 or 2 and you will pass. Some players play a more advanced version where they could bid 2 over 2 to show a weak hand with 4-4 in the majors, but that requires partnership agreement. 

3NT. When you have a source of tricks, you shouldn't get hung up on point count. Here, you are likely, at worst, to be  needing a helpful lead to make 9 or 10 tricks, and you might not even need the help. Don't transfer to diamonds if you always plan on playing in notrump (whether or not you play four-way transfers).

2NT. You don't have to have a balanced hand to bid 2NT here. You have an invitational hand and your only invitational bid is 2NT. 3 is game forcing. If partner had responded 2, you might have considered passing, since 3NT will likely be difficult with at most 4 hearts between the two hands. If 2 promises a major (which most play) then partner will know you have four spades. 

3. You'd like to use Blackwood, but 4NT here is quantitative (what if you had this same hand but with the 6 becoming the 6-- you'd use Stayman and then hope 4NT is quantitative). In order to set trump, make an "impossible" bid. You can't have long spades and no interest in hearts or you would have transferred. Bidding 3 of the other major is your way of setting trump after a Stayman auction. For the 4 bidders--I would treat this as a splinter. Gerber is baby food.

Pass. Sure, you have 8 points, but they are lousy (no aces, too many queens) and no spot cards higher than the eight. While there's an outside chance you have 25 points, it's not worth the risk of going down in either 2NT or 3NT. 

2. While you know you have a heart fit, you might also have a good spade fit. Often it will be better to play in a 4-4 or 5-4 fit than in a 6-2 fit. You find out by using Stayman. If partner answers in a major, raise to 4. If partner bids 2, players using Texas transfers should bid 4 which is delayed Texas. If not playing that, then responder can bid 4 (natural) after 1NT-2-2.