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Questions 3 and 4 are straightforward. This is (slightly) more interesting.

Difficulty 1 star
Comment We have tempai East dora 2. What to do?

Round East 3rd 1 honba dora is

East (You) 23700 points. You hand
Your discards are

South 28000. He has discarded

West 29100. he has discarded

North 30200. Discards are

damaten.

Double east dora 1 ron is 8000, great, and tsumo is 12000, perfect. Riichi is unnecessary overkill. The 4-7 wait is at full 8 tiles, while the 6m-6s is unlikely to be discarded at all. Because of the 8pin furiten, the only option to improve the shanpon is the 5-pin, for 9 tiles for now. It just isn't efficient.

Indeed silent tenpai.
Declaring riichi will reward more only in case of ron (or with ura dora of course), which is not very expectable considering we're waiting for tiles around the dora.

I agree with both of you it is what I would make too.

Totsugeki says: The options are dama, riichi, dama, riichi. Whether you go with the default that 3 han good wait should always be riichi, or you go with the scoring, there is no advantage with dama. Even if you dama it is not like the dora is going to come out quickly.

Which leaves riichi, and we need to choose between shampon wait or ryanmen. It more important to aim for top place by winning rather than aiming for haneman. As such, one should choose the ryanmen.

What if we didn't have but instead a closed triple of one of the other winds? Ryanmen riichi dora 1 vs shampon riichi dora 2 (or even dora 3)? In this case the extra dora doubles the score so there are no problem choosing shampon. Just because the ryanmen has twice the tiles to win on, that doesn't mean the overall win probability is double. This is even more so in the early game.

Lastly, suppose was the dora and we could choose sampon wait. In this case going for dora is also fine. Early game honour tile shampon wait has a similar win rate fail rate to ryanmen. Even if it is dora wait, its still greater than 60% this early in the game.