Learn Hardcore Russian: Вечером мне хочется, чтобы в доме был порядок. - In the evening I want there to be order in the house.

Russian often uses the instrumental case to express time when something happens: утром, днём, вечером, ночью, зимой.
So вечером literally means in the evening / in the evenings (depending on context), and it’s a fixed, very common pattern.

Does вечером mean “this evening” or “in the evenings (generally)”?

By itself, вечером is ambiguous: it can be either in the evening (at evening time) or (usually) in the evenings, depending on context.
If you want to be clearly habitual, Russian often uses по вечерам = in the evenings (as a habit).
If you want clearly “tonight/this evening,” you might use сегодня вечером.

Why is it мне хочется and not something like “I want” with я?

хотеться works like a “feeling/wanting happens to me” construction. The experiencer is in the dative: мне = to me.
So мне хочется is closer to I feel like… / I have the desire… than a direct, deliberate я хочу.

What’s the difference between мне хочется and я хочу here?

мне хочется: softer, more internal, like a mood or craving: I feel like / I’d like / I’m in the mood for.
я хочу: more direct and purposeful: I want (often sounds stronger, more intentional).
In this sentence, мне хочется, чтобы… sounds like a personal preference/need rather than a demand.

Why is чтобы used, and what does it mean in this structure?

чтобы introduces a clause expressing a desired result/state: I want (it) to be the case that…
So мне хочется, чтобы в доме был порядок = I feel like / I want there to be order in the house.

Why is there a comma before чтобы?

Because чтобы starts a subordinate clause (чтобы в доме был порядок), and Russian normally separates main and subordinate clauses with a comma: мне хочется, чтобы …

Why do we say в доме (prepositional) here?

в + prepositional is used for location: in the house.
So в доме = in the house / at home (in the house as a place).

Why is it был порядок and not есть порядок?

In the present tense Russian often omits to be: you’d usually say в доме порядок (no verb).
But after чтобы, Russian commonly uses быть in the past form to express the desired state:

чтобы был порядок (masc. порядок)
чтобы была тишина (fem. тишина)
It’s not past time here; it’s the standard form used in this kind of “desired/required” clause.

Could it also be чтобы в доме был порядок vs чтобы был порядок в доме? Is word order flexible?

Yes, word order is flexible. Both are grammatical:

чтобы в доме был порядок emphasizes the place (in the house).
чтобы был порядок в доме can put slightly more focus on порядок first, then specify where.
The original version sounds very natural and neutral.

What exactly does порядок mean here—“order” as in “command,” “sequence,” or “tidiness”?

In this context порядок means orderliness / tidiness / things being in proper condition—basically a clean, organized home.
It can also mean “order” in other senses, but в доме порядок almost always refers to tidiness/being in good order.

Why is порядок nominative? Shouldn’t it be something like an object?

Here порядок is the subject of был: (there) was order.
Russian often expresses “there is/are” as (location) + (subject):

В доме был порядок = There was order in the house / The house was in order.

Can this sentence imply “I want someone to keep it tidy,” or only “I want it to be tidy”?

Grammatically it only states the desired state: that there be order in the house.
It doesn’t explicitly say who should do it. Context can imply “someone should keep it tidy,” but the sentence itself focuses on the result (order), not the actor.

Is в доме the same as дома here?

Not exactly:

в доме = literally in the house (emphasizes the physical place).
дома = at home (more about being at home as a situation).
You can say чтобы дома был порядок and it’s common; it sounds slightly more general (“at home”) than “in the house.”