Una pregunta difícil me hizo cambiar el orden de las diapositivas.

Because pregunta is a feminine noun, even though it ends in -a, which is the usual feminine ending anyway. So it takes the feminine article una and the adjective also stays in the feminine form:

• una pregunta difícil

In this case, difícil looks the same for masculine and feminine, so only the article clearly shows the gender.

In Spanish, adjectives often come after the noun, especially when they are simply describing it in a normal, factual way.

So:

• una pregunta difícil = a difficult question

Putting the adjective before the noun is sometimes possible in Spanish, but it often changes the tone or emphasis. The normal order here is noun + adjective.

Me means to me or made me in this sentence. It is the direct object pronoun referring to the person affected by the action.

In:

• Una pregunta difícil me hizo cambiar...

the structure is:

• something made me do something

So me is the person who was caused to change the order of the slides.

Because object pronouns like me, te, lo, la, nos usually go before a conjugated verb in Spanish.

So:

• me hizo cambiar

not:

• hizo me cambiar

This is standard pronoun placement in Spanish.

Because hacer + infinitive is a very common way to express causing someone to do something.

• me hizo cambiar = it made me change

This is different from:

• me cambió = it changed me / changed something for me, depending on context

So hizo cambiar shows that the difficult question caused the speaker to change the order.

The pattern is:

• hacer + [person/object pronoun] + infinitive or
• [subject] + hacer + infinitive

In this sentence:

• Una pregunta difícil me hizo cambiar el orden de las diapositivas.

the parts are:

• Una pregunta difícil = what caused the action
• me = the person affected
• hizo = made
• cambiar = change

So literally, it is something like:

• A difficult question made me change the order of the slides.

This structure is very common in Spanish:

• Me hizo pensar. = It made me think.
• Nos hizo esperar. = It made us wait.

Because hizo is the preterite form of hacer for él/ella/usted.

Here, the subject is:

• Una pregunta difícil

That is grammatically third person singular, so Spanish uses:

• hizo

The preterite is used because it refers to a completed action in the past: the question caused the speaker to change the order.

Because after hacer in this causative structure, Spanish uses the infinitive:

• hizo cambiar
• hizo hablar
• hizo pensar

This is similar to English:

• made me change
• made me think

So cambiar stays in the infinitive because it depends on hizo.

Spanish often uses the definite article more often than English does.

So:

• el orden de las diapositivas

literally means:

• the order of the slides

Even if English might sometimes say change slide order, Spanish usually prefers the article here.

It means of the slides.

So:

• el orden de las diapositivas = the order of the slides

This is a very common Spanish pattern:

• el color del coche = the color of the car
• la puerta de la casa = the door of the house

Spanish often uses de where English might use of or sometimes a noun used as an adjective.

Yes. That is also correct.

• Una pregunta difícil me hizo cambiar el orden de las diapositivas.
• Una pregunta difícil hizo que cambiara el orden de las diapositivas.

Both mean roughly the same thing, but the structure is different.

1. hacer + infinitive

• me hizo cambiar
• more direct and compact
• very common in everyday Spanish

2. hacer que + subjunctive

• hizo que cambiara
• also common
• often sounds a little more explicit or formal

In your original sentence, me hizo cambiar is natural and efficient.

Because in English, after make, we actually do not use to:

• It made me change
  not
• It made me to change

Spanish works similarly here:

• me hizo cambiar

So cambiar appears directly after hizo, with no extra word.

Yes. Diapositivas can refer to presentation slides, including PowerPoint-style slides.

Historically, diapositiva also meant a photographic slide, but in modern contexts it very commonly means presentation slide.

So in this sentence, las diapositivas is naturally understood as the slides in a presentation.

Spanish word order is more flexible than English, but not every possible order sounds equally natural.

The most natural version here is:

• Una pregunta difícil me hizo cambiar el orden de las diapositivas.

You could move elements around for emphasis, but:

• Me hizo cambiar el orden de las diapositivas una pregunta difícil

sounds marked and unusual in normal conversation. It could work in special contexts, but it is not the neutral word order a learner should copy first.

The main conjugated verb is hizo.

Even though cambiar also expresses an action, it is in the infinitive, so it is not the main finite verb.

So the core structure is:

• Una pregunta difícil = subject
• me hizo cambiar... = predicate

The sentence is really about what the difficult question did: it made the speaker change something.