Learn Hardcore Indonesian: Rok adik perempuan saya pun sudah dicuci dan disetrika. - My younger sister’s skirt has also been washed and ironed.

It’s an additive/focus particle meaning “also/too” (and sometimes “even”). It follows the element being highlighted. In this sentence, pun puts focus on the whole noun phrase Rok adik perempuan saya, implying “that skirt as well.” If you drop pun, the sentence is still correct but loses the “also” nuance: Rok adik perempuan saya sudah dicuci dan disetrika.

Can I replace "pun" with "juga" or "bahkan"? What’s the difference?

juga = “also/too,” the most common and neutral choice. Typical placement is after the subject: Rok adik perempuan saya juga sudah dicuci dan disetrika.
bahkan = “even” (stronger emphasis than pun/juga). Place it before the focused element or before the predicate: Bahkan rok adik perempuan saya sudah dicuci dan disetrika. or Rok adik perempuan saya bahkan sudah dicuci dan disetrika.
pun is slightly more formal/literary and ties tightly to the focused constituent: Rok adik perempuan saya pun ...

Where can "pun" appear in the sentence?

Place pun immediately after the constituent you’re focusing. Here it follows the subject NP: Rok adik perempuan saya pun ... Don’t move it to the end of the clause. Patterns like sudah pun are old-fashioned/Malay; in standard modern Indonesian, prefer X pun sudah ...

Why use the passive voice (dicuci, disetrika)?

Indonesian often topicalizes the patient and omits the agent. Passive with di- does that naturally. Active and other alternatives:

Active: Ibu sudah mencuci dan menyetrika rok adik perempuan saya.
Passive type I (with an agent): Rok adik perempuan saya sudah dicuci dan disetrika oleh Ibu.
Colloquial passive with sama: Rok adik perempuan saya sudah dicuci dan disetrika sama Ibu.
Passive type II (agent before bare verb): Rok adik perempuan saya sudah Ibu cuci dan setrika.

Do I need the prefix "di-" on both verbs?

Yes. Keep di- on each passive verb: ... dicuci dan disetrika. Don’t say dicuci dan setrika. You can add a sequencer: dicuci lalu disetrika or dicuci kemudian disetrika.

Does "dan" imply the actions happened in that order?

No. dan simply joins two predicates. Real-world knowledge suggests wash before iron, but the grammar doesn’t force an order. To make the sequence explicit, use lalu/kemudian or a subordinate clause:

Rok ... sudah dicuci, lalu disetrika.
Setelah dicuci, rok ... disetrika.

What does "sudah" express? Could I use "telah" or "udah"?

sudah marks aspect (“already”), not tense. Alternatives:

telah = formal/literary: ... telah dicuci dan disetrika.
udah = colloquial spoken form of sudah: ... udah dicuci dan disetrika. Negative counterpart: belum (“not yet”): ... belum dicuci.

Is "adik perempuan saya" the normal way to say “my younger sister”?

Yes. adik = younger sibling (gender-neutral), perempuan specifies female. Variants:

adik saya (gender ambiguous)
Colloquial: adik cewek saya
Not natural: adik wanita saya
For “older sister,” use kakak perempuan saya.

How is possession formed in "Rok adik perempuan saya"?

Indonesian places the possessor after the noun: head noun + possessor. So rok adik perempuan saya = “my younger sister’s skirt.” Other examples: rumah saya (“my house”), buku adik saya (“my younger sibling’s book”).

Can I use -nya, milik, or punya to mark possession?

-nya can mark definiteness/specificity: Roknya adik perempuan saya pun ... (emphasizes “the skirt”).
milik is formal: Rok milik adik perempuan saya ...
punya is colloquial “belong to”: Ini rok punya adik perempuan saya. As a modifier inside a NP, punya is informal: rok punya adik perempuan saya (fine in speech, avoid in formal writing).

Is "rok" singular or plural here? How do I make it plural?

Without a number or quantifier, rok can be interpreted as singular or plural from context. To make it clearly plural:

Reduplication: rok-rok adik perempuan saya
Quantifiers: beberapa rok, banyak rok, semua rok
Verbs don’t change: Semua rok adik perempuan saya sudah dicuci dan disetrika.

Could I use "ter-" forms like "tercuci" or "tersetrika" instead?

Generally no, not for this meaning. ter- often marks a state/result or unintentional/accidental action. sudah dicuci/disetrika is the standard way to say the actions have been done. Forms like tercuci/tersetrika can sound odd or imply a state/accident rather than a deliberate completed action.

How would I include the agent naturally?

Neutral/formal: ... sudah dicuci dan disetrika oleh Ibu.
Colloquial: ... sudah dicuci dan disetrika sama Ibu.
Passive type II: ... sudah Ibu cuci dan setrika.
Active: Ibu sudah mencuci dan menyetrika ...

Do I need "yang" between "rok" and "adik perempuan saya"?

No. yang introduces relative clauses or marks a focused descriptor, not simple possession. Rok adik perempuan saya is correct for “my younger sister’s skirt.” With yang, you’d create a relative clause, e.g. rok yang adik perempuan saya pakai (“the skirt that my younger sister wears”).

Why is it "disetrika" and not something like "di-setrika" or "dinyetrika"?

The base is setrika (“iron”). Passive is di- + setrika → disetrika. The active is menyetrika (not “mengsetrika”). Writing di-setrika with a hyphen is sometimes seen informally, but standard spelling is disetrika.