kakutyouban ni yotte, seigenzikan ga kawaru.

A natural reading is:

かくちょうばん に よって、せいげんじかん が かわる。

Word by word:

• 拡張版 = かくちょうばん
• によって
• 制限時間 = せいげんじかん
• が
• 変わる = かわる

拡張版 literally means expanded version, expansion version, or extended edition.

Depending on context, it could mean:

• a game expansion
• a special/expanded release
• a version with added content

So in this sentence, it refers to the version/edition that affects the time limit.

Here, によって means something like:

• depending on
• according to
• varying with
• because of differences in

So 拡張版によって、制限時間が変わる means the time limit is not the same in every version; it changes depending on which expansion/version you mean.

This is one of the common uses of によって:

• A によって B が変わる = B changes depending on A

Not exactly.

• で often marks a means, method, or place.
• によって here emphasizes variation depending on a condition.

So:

• 拡張版によって、制限時間が変わる = The time limit changes depending on the expansion version.

If you replaced it with で, it would sound unnatural in this meaning.

が marks 制限時間 as the thing that changes.

So the structure is:

• 拡張版によって = depending on the expansion version
• 制限時間が = the time limit
• 変わる = changes

In other words, what changes?
→ the time limit

That is why が is natural here.

Because 変わる is an intransitive verb: it means to change.

• 制限時間が変わる = The time limit changes

By contrast, 変える is transitive: to change something.

• 制限時間を変える = to change the time limit

This sentence is describing a change happening to the time limit, not directly saying who changes it, so 変わる is the correct choice.

Yes, Japanese does not need to state the agent here.

The sentence focuses on the result:

• the time limit changes depending on the expansion version

It does not explicitly say:

• who designed it
• who changed it
• what system is changing it

That kind of information is often omitted in Japanese when it is not important or is already understood from context.

Grammatically, that is possible as a very literal translation, but it sounds unnatural in English.

Better translations are:

• The time limit changes depending on the expansion version.
• The time limit varies by expansion version.
• The time limit differs depending on the version.

So the Japanese is fine, but English usually prefers depending on or varies by here.

The structure is:

[condition/source of variation] によって、 [thing] が [intransitive verb]

In this sentence:

• 拡張版によって = depending on the expansion version
• 制限時間が = the time limit
• 変わる = changes

So the whole sentence is built as: Depending on the expansion version, the time limit changes.

The comma is just a pause marker. It helps separate the introductory phrase:

• 拡張版によって、 = depending on the expansion version,
• 制限時間が変わる。 = the time limit changes.

It is helpful for readability, but not always strictly required. You may also see:

拡張版によって制限時間が変わる。

with no comma.

Yes, but it would slightly change the nuance.

• 制限時間が変わる: focuses more directly on the time limit changes
• 制限時間は変わる: puts the time limit in topic position, often with contrast or emphasis

For example, は might suggest something like:

• As for the time limit, that changes (though maybe other things do not).

In a neutral statement like this, が is the most straightforward choice.

No. によって has several common meanings, including:

• by someone/something
  
  • ピカソによって描かれた = painted by Picasso
• by means of / through
  
  • 努力によって成功した = succeeded through effort
• depending on / according to
  
  • 人によって考え方が違う = ways of thinking differ depending on the person

In your sentence, it is the depending on / varies by meaning.

No, that would mean something different.

• によって = depending on / by / due to
• によると = according to

So:

• 拡張版によって、制限時間が変わる。
  = The time limit changes depending on the expansion version.

But:

• 拡張版によると…
  would mean according to the expansion version..., which does not fit this idea.

Yes, it is natural and grammatically complete.

It sounds like a factual statement you might see in:

• game rules
• product descriptions
• manuals
• comparison charts

A very natural English-like paraphrase would be:

• The time limit varies depending on the expansion version.

So as Japanese, the sentence is short, clear, and normal.