रात को माँ ने दरवाज़ा खोला और चाय बनाई।

Here को is marking a time expression, not a direct object.

रात को is a very common way to say at night.
So in this sentence, रात को works like an adverbial phrase telling you when the actions happened.

A few similar examples:

• सुबह को — in the morning
• शाम को — in the evening
• सोमवार को — on Monday

So को does more than one job in Hindi; here it is not the usual object-marker meaning.

ने is the ergative marker. In standard Hindi, it is commonly used with the subject of a perfective transitive verb.

In this sentence:

• खोला = opened
• बनाई = made

Both are completed actions, and both verbs are transitive, so the subject माँ takes ने.

So:

• माँ ने = mother (as the doer of these completed actions)

This is one of the most important patterns in Hindi past/perfective sentences.

Because both verbs share the same subject: माँ.

Hindi does not need to repeat माँ ने before the second verb if the subject is clearly the same.

So this:

• रात को माँ ने दरवाज़ा खोला और चाय बनाई।

means:

• Mother opened the door and made tea.

A more repetitive version would still be understandable, but it would sound unnecessary:

• रात को माँ ने दरवाज़ा खोला और माँ ने चाय बनाई।

Normally, Hindi avoids that repetition.

Because with ने in a perfective transitive clause, the verb often agrees with the direct object, not the subject.

Here the direct object is दरवाज़ा, which is:

• masculine
• singular

So the verb becomes:

• खोला = masculine singular

That is why it does not match माँ.

A very important idea:

• without ने, learners often expect the verb to agree with the subject
• with ने
  • perfective transitive verb, agreement often shifts to the direct object

For the same reason: the verb is agreeing with the direct object.

The direct object here is चाय, which is:

• feminine
• singular

So the verb form is:

• बनाई = feminine singular

Compare:

• चाय बनाई — made tea
• खाना बनाया — made food

Because चाय is feminine but खाना is masculine, the verb form changes.

Yes. More specifically, it uses the perfective form, which in this kind of sentence is typically understood as a completed past action.

So:

• खोला = opened
• बनाई = made

The sentence presents two finished actions in sequence:

1. the door was opened
2. tea was made

For a learner, it is fine to think of this as a normal past-time sentence, though grammatically Hindi often explains it in terms of aspect as well as tense.

Because direct objects in Hindi are often left unmarked, especially when they are inanimate and there is no special need to mark them.

So:

• दरवाज़ा खोला is completely normal.

Hindi uses को much more often with:

• people
• animate beings
• specific or affected objects in some contexts

But many ordinary inanimate direct objects appear without को.

Also, the lack of को is important here because it allows the verb खोला to agree with दरवाज़ा.

Hindi does not have articles like English a/an and the.

So:

• दरवाज़ा can mean a door or the door
• चाय can mean tea, some tea, or the tea, depending on context

The listener understands the intended meaning from the situation, not from an article.

That is why a Hindi sentence can look shorter than the English translation.

Yes, often it could.

Both रात को and रात में can refer to night time, but रात को is a very common everyday way to say at night.

Very roughly:

• रात को — at night
• रात में — in the night / during the night

In many real-life contexts, the difference is small and both are natural. In this sentence, रात को sounds perfectly normal.

Their dictionary forms are:

• खोलना — to open
• बनाना — to make

In the sentence, these appear in perfective forms:

• खोला ← from खोलना
• बनाई ← from बनाना

You can think of them as forms built from the verb stem and changed to match gender/number agreement.

So a useful pattern is:

• खोलना → खोला / खोली / खोले
• बनाना → बनाया / बनाई / बनाए

The word order here is very natural, but Hindi is more flexible than English.

This sentence follows a common pattern:

• time expression
• subject
• object
• verb
• और
• object
• verb

So:

• रात को — time
• माँ ने — subject
• दरवाज़ा खोला — first action
• और — and
• चाय बनाई — second action

You could also say:

• माँ ने रात को दरवाज़ा खोला और चाय बनाई।

That would still be correct. The difference is mainly one of emphasis and style, not basic meaning.