Preguntó por mi edad.

Preguntó is the third-person singular preterite of preguntar.

That means it usually translates as he asked, she asked, or you (formal) asked, referring to a completed action in the past.

• pregunto = I ask
• preguntaba = he/she was asking / used to ask
• preguntó = he/she asked

The accent mark on -ó is important because it shows both the pronunciation and the tense.

Spanish often leaves out the subject pronoun when it is clear from the verb form or the context.

So Preguntó by itself can mean:

• he asked
• she asked
• you asked (formal usted)

Spanish does not need to say él, ella, or usted unless the speaker wants to emphasize it or avoid confusion.

So the sentence could be understood as:

• He asked about my age
• She asked about my age
• You asked about my age (formal)

Context tells you which one is meant.

In Spanish, preguntar por is a common structure meaning to ask about or sometimes to ask for.

So in Preguntó por mi edad, por connects the verb to the thing being asked about: my age.

This is something English speakers often need to learn as a fixed pattern:

• preguntar por alguien/algo = to ask about someone/something

Examples:

• Preguntó por ti. = He/She asked about you.
• Preguntaron por el director. = They asked for / asked about the director.

You usually cannot translate por word for word here. It is just part of the Spanish expression.

This is a very useful distinction.

• Preguntó por mi edad = He/She asked about my age
• Me preguntó mi edad = He/She asked me my age

The second version is more direct and often closer to the English idea of asking someone their age.

So:

• preguntar por + noun = ask about something
• preguntar + direct object / indirect object structure = ask someone something

Compare:

• Preguntó por mi edad. = He/She asked about my age.
• Me preguntó mi edad. = He/She asked me my age.
• Me preguntó cuántos años tenía. = He/She asked me how old I was.

Yes. Preguntar por can mean either ask about or ask for, depending on context.

Examples:

• Preguntó por mi edad. = He/She asked about my age.
• Preguntó por el médico. = He/She asked for the doctor.
  or sometimes asked about the doctor, depending on context.

So the meaning depends on what follows and the situation.

With mi edad, the meaning is clearly ask about my age, not ask for my age in a literal sense.

Because mi here is a possessive adjective, meaning my.

• mi edad = my age

The form mí with an accent is a pronoun meaning me after a preposition:

• para mí = for me
• sin mí = without me

So:

• mi edad = correct
• mí edad = incorrect

A useful shortcut:

• mi = my
• mí = me

Edad means age, so mi edad literally means my age.

Spanish can also talk about age using años in other structures, especially with tener:

• Tengo 20 años. = I am 20 years old.
• ¿Cuántos años tienes? = How old are you?

But in this sentence, the noun being discussed is edad, which is perfectly natural:

• Preguntó por mi edad. = He/She asked about my age.

So Spanish uses both:

• edad as the abstract noun age
• años when stating how many years old someone is

Yes, it is completely normal.

The basic structure is:

• Verb + por + noun phrase

So:

• Preguntó = asked
• por mi edad = about my age

Spanish word order is often flexible, but this is the most straightforward order here.

You could add a subject if you wanted:

• Ella preguntó por mi edad.
• Mi vecino preguntó por mi edad.

But without a subject, the sentence is still natural and complete.

The accent mark shows that the stress falls on the last syllable: pre-gun-TÓ.

It also helps distinguish preguntó from pregunto:

• pregunto = I ask
• preguntó = he/she asked

So the accent is not optional. It changes both pronunciation and meaning.

Yes, it is grammatically natural in Spain as well as in other varieties of Spanish.

That said, in everyday conversation, speakers might sometimes use a more direct structure if they mean someone actually asked them their age:

• Me preguntó mi edad.
• Me preguntó cuántos años tenía.

So Preguntó por mi edad is correct and natural, but it can sound a little more like asked about my age than asked me how old I was.

A simple pronunciation guide is:

preh-goon-TOH por mee eh-DAHD

A bit more accurately:

• Preguntó → stress on the last syllable
• por → short and simple
• mi → like mee
• edad → stress on the second syllable: e-DAD

In Spain, the pronunciation of z and c before e/i is different, but this sentence does not contain those sounds, so nothing especially Spain-specific changes here.