बचपन में मैं गाँव में रहती थी।

Because they belong to two different phrases:

• बचपन में = in childhood / during childhood
• गाँव में = in the village

In Hindi, में is a postposition meaning in, inside, or sometimes during, depending on context. So the sentence literally has:

• बचपन में → during childhood
• मैं → I
• गाँव में → in the village
• रहती थी → used to live / lived

So using में twice is completely normal here.

बचपन means childhood.
With में, it becomes in childhood or during childhood.

So:

• बचपन = childhood
• बचपन में = in childhood / when I was a child

This is a very common way to talk about a period of life in Hindi.

Because the speaker is feminine.

In Hindi, the verb form often reflects the gender of the subject in sentences like this:

• मैं ... रहती थी = I used to live ... (female speaker)
• मैं ... रहता था = I used to live ... (male speaker)

So:

• रहती = feminine singular
• थी = feminine past form of to be

If a man were speaking, the sentence would be:

बचपन में मैं गाँव में रहता था।

Here रहती थी means used to live or lived in the sense of an ongoing past situation.

It is built from:

• रहना = to live, to stay
• रहती = living / used to live (feminine form)
• थी = was

Together, रहती थी expresses a past habitual or continuing state. In natural English, this is often translated as:

• I used to live in the village in childhood
• I lived in the village when I was a child

No, they are different.

• रहती थी usually suggests a habitual or continuing situation in the past:
  I used to live / I lived
• रही थी is the past progressive/perfective-type form and would sound different in meaning and usage.

For example:

• मैं गाँव में रहती थी = I used to live in the village / I lived in the village
• मैं गाँव में रह रही थी = I was living in the village

So in your sentence, रहती थी is the correct form for a general past situation during childhood.

Because Hindi normally follows Subject–Object/Other elements–Verb word order, often called SOV.

This sentence is arranged like this:

• बचपन में = time expression
• मैं = subject
• गाँव में = location
• रहती थी = verb

So the verb naturally comes at the end. That is one of the most important differences from English.

Yes, to some extent. Hindi word order is flexible, especially with time and place phrases, but the verb usually stays at the end.

For example, these can all work depending on emphasis:

• बचपन में मैं गाँव में रहती थी।
• मैं बचपन में गाँव में रहती थी।
• मैं गाँव में बचपन में रहती थी। ← possible, but less natural

The most natural version is usually the original one, because it introduces the time first: during childhood.

गाँव is pronounced approximately like gaãv.

A few key points:

• गा sounds like gaa
• ँ shows nasalization, so the vowel is nasalized
• व here sounds somewhere between English v and w, depending on accent and speaker

So गाँव is often approximated as gaaon or gaãv, but the important thing is the nasalized vowel.

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

So गाँव can mean:

• village
• a village
• the village

The exact meaning depends on context. In translation, English usually adds the or a where needed, but Hindi does not need a separate word for that.

Yes, often it can be omitted if the subject is already clear from context.

For example:

• बचपन में गाँव में रहती थी।

This can still mean I used to live in the village in childhood, especially if it is already obvious who is speaking.

Hindi often drops pronouns when they are understood. However, including मैं is perfectly natural and often helpful for clarity or emphasis.

Because ने is not used with every past sentence.

ने usually appears with many perfective transitive verbs, especially when the subject did an action to something. But रहना here is not being used that way.

So:

• मैं गाँव में रहती थी। = correct
• मैंने गाँव में रहती थी। = incorrect

This is a very common thing for learners to notice: not every past sentence takes ने.

A male speaker would say:

बचपन में मैं गाँव में रहता था।

The only changes are in the verb:

• feminine: रहती थी
• masculine: रहता था

Everything else stays the same.

The dictionary form is रहना, which means to live, to stay, or to reside.

From रहना, you get forms like:

• रहता = masculine singular
• रहती = feminine singular
• रहते = masculine plural / respectful

In your sentence, रहती is used because the speaker is feminine and singular.