Я не люблю возвращаться домой затемно.

After любить / не любить, Russian usually uses an infinitive to say what someone likes or does not like doing:

• Люблю читать = I like reading
• Не люблю ждать = I don't like waiting

So не люблю возвращаться means I don’t like returning / coming back.

This is about aspect.

• возвращаться = imperfective
• вернуться = perfective

With не люблю, Russian normally uses the imperfective when talking about a general preference or dislike, especially for repeated or habitual actions. The sentence means that, in general, the speaker does not like the experience of coming home when it is dark.

So:

• Я не люблю возвращаться домой затемно = natural
• Я не люблю вернуться домой затемно = not natural here

The imperfective fits the idea of something I generally dislike doing.

The -ся makes the verb reflexive, and in this case it is the normal Russian way to say to return / to come back.

Compare:

• возвращать = to return something, to give something back
• возвращаться = to return, to come back

So:

• Я возвращаю книгу = I’m returning the book
• Я возвращаюсь домой = I’m returning home

English uses the same word return for both ideas, but Russian often separates them this way.

Because домой expresses movement toward home, while дома means at home.

• идти домой = to go home
• возвращаться домой = to return home
• быть дома = to be at home

So after a verb of motion like возвращаться, домой is the correct choice.

For most learners, it is best to think of домой as a fixed adverb meaning homeward / to home rather than as a normal modern case form.

That is why it behaves differently from ordinary noun forms like:

• дом = house/home
• дома = at home
• к дому = toward the house

So in возвращаться домой, just learn домой as the standard word used with motion toward home.

Here затемно means when it is already dark, so in natural English this is usually after dark.

In other contexts, затемно can also mean while it is still dark, for example before dawn. But in this sentence, because we are talking about returning home, the natural meaning is:

• coming home after dark
• returning home when it’s already dark outside

So context tells you which shade of meaning is intended.

It is an adverb. It is not extremely rare, but it can sound a bit more literary or concise than a longer phrase like:

• когда уже темно
• в темноте
• после наступления темноты

Still, it is perfectly understandable and natural. A useful opposite word is засветло, meaning before it gets dark / while it is still light.

Because домой itself already contains the idea of direction. Russian often uses directional adverbs without a preposition:

• домой = home
• туда = there
• сюда = here

So возвращаться домой is the normal idiomatic expression.

If you said к дому, that would mean toward the house/building, not necessarily home in the personal sense.

Yes. In many contexts, that is the most natural English translation.

Russian возвращаться домой literally emphasizes returning back home, but English often just says come home:

• Я не люблю возвращаться домой затемно
  = I don't like coming home after dark

A close Russian alternative is приходить домой, which focuses more on arriving home. Возвращаться домой specifically keeps the idea of coming back.

Not strictly. Russian often drops subject pronouns when the verb ending already makes the subject clear.

So both are possible:

• Я не люблю возвращаться домой затемно
• Не люблю возвращаться домой затемно

The version with я is still very normal. It can make the sentence feel a bit more explicit, or simply serve as a neutral sentence opening.

Yes. Russian word order is flexible, and changing it usually changes emphasis rather than the basic meaning.

Neutral order:

• Я не люблю возвращаться домой затемно.

If you want to emphasize after dark, you could move затемно earlier:

• Я не люблю затемно возвращаться домой.
• Затемно я не люблю возвращаться домой.

The original sentence is a very natural, neutral way to say it.