For landed property structural issues, like cracks, sinking building, is it under the purview of the developer, house owner, or municipal council?

Ordinary wall crack, land sinking /= structural issue.

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Rather not ordinary, though. One of the beams at my porch (the one next to the public drain) is uplifted, making the fence that hold on to it to tercabut, and i suspect this is what's causing the cracks on the sec9nd floor roof

Is between dev and municipal councillor contractor issue.
Depend who did not go by the book. But house owner have to take up the burden and loss.

You mean that the house owner would foot the bill? Not sure if pursuing this matter would solve the issue

whoever at fault will foot the bill (developer vs drain contractor) but the homeowner will go through the legal process or awaiting legal process between the 3 parties (developer vs drain contractor vs mc). The homeowner can foot the bill 1st and proceed request compensation later or wait for the result. Either way, the homeowner is at losing side.

If new house still within 24 months of VP, still under developer's defects liability period.

For certain defects (latent defects - which cannot be detected by reasonable inspection, compared to patent defects) even after DLP it may still be the developer's responsibility. But this one is much more complicated.

And if you do any kind of renovation, usually the court/arbitrator will deem that you have modified the original building and void the developer's DLP.

You may want to seek advise from PAM (they have bi-monthly 'architect meet the public session' to address this kind of issues, with engineer representing BEM together) You may also need to pay an independent building inspector to carry out a thorough inspection and produce a report to ensure you have a case.