Me levanto antes que mi hermana.

Because levantarse (to get up) is a reflexive verb in Spanish.

• Levantarse = to get oneself up / to get up (from bed)
• Levantar (without se) = to lift / to raise (something else)

So you need a reflexive pronoun:

• Yo me levanto – I get up
• Tú te levantas – You get up
• Él/Ella se levanta – He/She gets up, etc.

If you say “yo levanto” without me, it means I lift / I raise (something), not I get up:

• Yo levanto la caja. – I lift the box.

No. The subject is “yo” (even if it’s not written).
The “me” is a reflexive pronoun that shows the action comes back to the same person who does it.

• (Yo) me levanto. → I (subject) get myself up (object = me).

Spanish needs this pronoun with reflexive verbs like levantarse, vestirse, ducharse, sentarse, etc.
English often doesn’t show it (you usually don’t say “I get myself up” — just “I get up”), but Spanish must keep me / te / se / nos / os / se.

Yes. That’s perfectly correct.

• Me levanto antes que mi hermana.
• Yo me levanto antes que mi hermana.

Both mean the same thing.
Adding “yo” just adds a bit of emphasis on I (as opposed to someone else):

• Yo me levanto antes que mi hermana, pero ella se acuesta más tarde.
  I get up earlier than my sister, but she goes to bed later.

Because it’s a comparison between two people doing the same action.

In standard grammar:

• Use antes que when you’re comparing subjects / people:

  • Me levanto antes que mi hermana.
    I get up earlier than my sister.
  • Sale antes que yo.
    He leaves earlier than me.

• Use antes de for time / moments / infinitives:

  • Antes de las ocho. – Before eight o’clock.
  • Antes de salir. – Before leaving.

In real life, many native speakers do say “antes de mi hermana”, but “antes que mi hermana” is the more careful, recommended form for this kind of comparison.

It’s very common in speech and most people will understand it without a problem. Many natives say it.

However, in careful / formal Spanish, for comparing when two people do the same action, “antes que” is preferred:

• Recommended: Me levanto antes que mi hermana.
• Very common but less recommended in grammar books: Me levanto antes de mi hermana.

If you’re studying “correct” or exam Spanish, use antes que here.

• mi (no accent) = my, a possessive adjective:

  • mi hermana – my sister
  • mi casa – my house

• mí (with accent) = me, a stressed pronoun used after prepositions:

  • para mí – for me
  • sin mí – without me

In “mi hermana” you are saying “my sister”, so you need mi (no accent).

Yes, that’s correct, just less typical for this simple sentence.

Possible orders:

• Me levanto antes que mi hermana. (most natural)
• Antes que mi hermana, me levanto. (correct, a bit more literary/emphatic)
• Yo me levanto antes que mi hermana. (adds emphasis on I)
• Me levanto yo antes que mi hermana. (strong emphasis on I vs. others)

Word order is fairly flexible in Spanish, but the original order is the most neutral and common here.

• Me despierto = I wake up (I stop sleeping, but I might still be in bed).
• Me levanto = I get up (I physically get out of bed / stand up).

Example daily routine:

• Me despierto a las siete, pero me levanto a las siete y cuarto.
  I wake up at 7, but I get up at 7:15.

In your sentence, “Me levanto antes que mi hermana” is about the act of getting up, not just waking up.

Yes.

• Me levanto antes que mi hermana. – I get up earlier than my sister.
• Me levanto antes que ella. – I get up earlier than her.

Both are fine. Use mi hermana if you’re introducing who she is, and ella if it’s already clear from context who you’re talking about.

In Spanish, you don’t normally put an article (el, la, los, las) before a possessive adjective (mi, tu, su, nuestro…) in this kind of phrase.

Correct:

• mi hermana – my sister
• mi padre – my father
• mis amigos – my friends

Incorrect in standard Spanish:

• ✗ la mi hermana
• ✗ el mi padre

So “Me levanto antes que mi hermana” uses the normal pattern: mi + noun, without an article.