Learn Hardcore Indonesian: Apartemen yang mana sih yang paling dekat dengan stasiun? - Which apartment is the closest to the station?

yang introduces a clause that describes or identifies a noun (like “the one that…”).
First yang is part of the fixed phrase yang mana (“which one”).
The second yang introduces the identifying clause yang paling dekat dengan stasiun (“that is the closest to the station”).
In everyday speech people more often say: Apartemen mana yang paling dekat dengan stasiun? (only one yang).

What does sih add? Is it necessary or rude?

sih is an informal particle that adds nuance: soft insistence, curiosity, or mild impatience (“so, which one actually?”).
It’s not rude by itself, but tone matters. In formal or written contexts, omit it.
Without it the sentence is perfectly fine and more neutral.

Is Apartemen yang mana correct? I thought it should be Apartemen mana.

Both occur. Apartemen mana is the default and most common.
Apartemen yang mana often implies choosing from a visible/known set and sounds a bit more pointed or conversational, especially with sih.
For neutral style, prefer: Apartemen mana yang paling dekat dengan stasiun?

Why does mana come after the noun?

In Indonesian, “which” is expressed with post-nominal mana: noun + mana (e.g., apartemen mana, bus mana, orang mana).
If you insert yang, it still follows the noun: apartemen yang mana.

Can I drop the second yang before paling dekat?

In casual speech: yes. Apartemen mana paling dekat dengan stasiun? is common.
In careful or written Indonesian, keep it: Apartemen mana yang paling dekat dengan stasiun?

What’s the difference between paling dekat and terdekat?

They’re equivalent superlatives.
paling + adjective = analytic superlative: paling dekat.
ter- + adjective = synthetic superlative: terdekat.
All of these are fine:
- Apartemen mana yang paling dekat dengan stasiun?
- Apartemen mana yang terdekat dengan stasiun?

Which preposition goes with dekat: dengan, ke, or dari?

Standard: dekat dengan
- noun. Example: dekat dengan stasiun.
Also common: di dekat + noun (“near the station”): di dekat stasiun.
Avoid dekat ke in standard Indonesian.
dekat dari is often heard but considered nonstandard; use it only in set contrasts like tidak jauh dari stasiun (“not far from the station”), not with dekat itself.

Is a copula like adalah needed here?

No. Indonesian questions and noun-modifying clauses don’t need a copula.
Use adalah in statements that equate things: Apartemen yang paling dekat dengan stasiun adalah Tower A.

Should I say stasiun or stasiunnya?

stasiun is fine; definiteness is usually clear from context.
stasiunnya can mark a specific, known station (“the station we’ve been talking about”) or “its station” depending on context.
In most questions like this, stasiun (without -nya) is the default.

Is the whole sentence informal? How would I make it neutral or formal?

The original with sih is informal conversation.
Neutral/formal: Apartemen mana yang paling dekat dengan stasiun?
For very formal writing, you could also use terdekat or manakah: Apartemen manakah yang terdekat dengan stasiun?

Can I front the descriptive part for emphasis?

Yes, topicalization is natural:
- Yang paling dekat dengan stasiun, apartemen yang mana (sih)?
This highlights the criterion first (“the one closest to the station”).

Do I ever need a classifier like buah with apartemen here?

Not in this question. Apartemen mana… is correct.
A classifier like sebuah appears when counting or introducing one apartment: sebuah apartemen baru (“a new apartment”).

How would I ask a comparative instead of a superlative?

Use lebih (“more”):
- Apartemen mana yang lebih dekat dengan stasiun, A atau B?
- Or simply: Mana yang lebih dekat dengan stasiun, A atau B?

Any quick pronunciation tips for tricky words here?

Is yang here like English “that/which/who,” or something else?

Yes, yang is the particle that turns a phrase into a noun-modifying clause (“the one that/which…”).
It also works as a focus marker when fronted: Yang paling dekat (adalah) Apartemen A.