Endymion77

I would take 1M - 2m - 4m as showing this type of hand, and 1M - 2m - 4M as denying fit and minimum (4 controls or less). That seems more traditional to me.

I wouldn't, I would pull to 2♥

2♥ as a good spade raise seems right, and I'd pass 2♠ by partner

You're way too strong for a splinter. Start with 2♥, partner might surprise you by raising. If not, set spades as trump with 3♠ and see if partner can bid a Serious 3NT or give you a courtesy cue bid. Knowing about your major-oriented hand will surely help him re-evaluate his holding.

I would consider this a Lebensohl situation, and proceed like after a direct 2♠ overcall

Sigh, double and get +300

Diamonds at IMPs / Spade at MPs for me

♠A

You have the best possible hand for the sequence so you have to bid 4♠ but it's a real mystery why partner passed 2♥

It's a rather common agreement to play 1 and 3 level bids as advancer forcing, and 2-level bids non-forcing constructive but I've seen virtually every possible configuration so you have to discuss this with partner.

Your partner: he should correct 2♦ to 2♠. 2NT is unbelievable. You: 2♦ is an underbid but is surely better than a 2♠ rebid (I would rate 2♦ 4/10 and 2♠ 1/10 for opener's rebid).

If you have only a small amount of time (say 30-60 minutes before the session), agree on a basic system (e.g. 2/1 with Bergen raises) in the first 2 minutes and then talk about defense (leads and signals).

East is 100% to blame. After West bids freely, 2♠ is merely competitive (especially at MPs there's a case to be made that it shouldn't promise any extra values at all). The initial double is OK but I would bid 2♦ over 2♣ (3♣ would be a slight overbid, and 2♥ is natural like 2♦ so it's out of the question).

You can have 4153, or 4144, or 4054, or 4063. What's important is the heart shortness which you would like to show. I guess it's a language issue and it's not "patterning out", no problem. BTW with responder's hand I wouldn't accept over 3♣ - very weak spades when we know we only have a 4-4 fit (so it can become rather ugly), too much in hearts, and it's MPs.

I would pattern out with 3♣ in case partner has nothing in hearts but it's close (mainly because it's possible that 3♠ is a trick too high which would be a MP disaster)