Реальность оказалась сложнее.

Оказалась comes from оказаться, which means to turn out (to be) or to prove to be.

So:

• Реальность была сложнее = Reality was more complex
• Реальность оказалась сложнее = Reality turned out to be more complex

The version with оказалась suggests a result that became clear later, often with a sense of surprise, contrast, or corrected expectation.

Because the subject, реальность, is a feminine singular noun.

In the past tense, Russian verbs agree with gender and number:

• оказался = masculine
• оказалась = feminine
• оказалось = neuter
• оказались = plural

Since реальность is feminine, the verb must be оказалась.

Сложнее is the comparative form of сложный (complex, difficult, complicated).

So:

• сложный = complex
• сложнее = more complex

This is the simple comparative form. In Russian, this form does not change for gender, number, or case.

That means the same сложнее can be used with masculine, feminine, neuter, or plural subjects.

In Russian, the thing being compared to is often left unstated if it is obvious from context.

So Реальность оказалась сложнее literally means Reality turned out more complex, with the comparison understood as something like:

• than expected
• than we thought
• than it seemed
• than the theory

If you want to make it explicit, you can add it:

• Реальность оказалась сложнее, чем мы думали.
  Reality turned out to be more complex than we thought.

Not necessarily. Сложный and сложнее can mean several related things:

• more complicated
• more complex
• more difficult

With реальность, more complex is often the most natural translation, because it suggests that reality is not as simple as expected.

So the exact English word depends on context.

It is in the nominative case, because it is the subject of the sentence.

• Реальность = the thing that turned out to be something

The structure is basically:

• Subject
  • verb
    • comparative predicate

So:

• Реальность = subject
• оказалась = verb
• сложнее = predicate complement in comparative form

Not in this exact structure.

After оказаться, Russian normally uses either:

1. a short adjective
2. a comparative form like сложнее

So this sentence works naturally as:

• Реальность оказалась сложнее.

If you use более сложной, that would be instrumental feminine singular, and it would not fit naturally here by itself.

You could say something like:

• Реальность оказалась более сложной, чем мы думали.

That is possible, but сложнее is shorter and usually more natural in this kind of sentence.

Both can express comparison, but they work differently.

• сложнее = simple comparative, very common and compact
• более сложной = analytic comparative-like structure with более, but the adjective still agrees in form with the syntax of the sentence

In this sentence, сложнее sounds especially natural because Russian often prefers the simple comparative in short statements like this.

So:

• Реальность оказалась сложнее. = very natural
• Реальность оказалась более сложной. = possible, but a bit heavier in style

Yes. Оказаться is perfective.

That matters because the sentence describes a completed realization or result: at some point, it became clear that reality was more complex.

Its imperfective partner is оказываться:

• Реальность оказывалась сложнее.

That version would suggest repeated situations, a background description, or something that kept turning out that way in different cases.

In this sentence, оказалась is used because we are talking about one concluded outcome.

Yes, Russian word order is flexible, though the emphasis changes.

Neutral order:

• Реальность оказалась сложнее.

Possible alternatives:

• Сложнее оказалась реальность.
• Оказалась сложнее реальность.

These are more marked and may sound literary or emphatic, depending on context.

The original order is the most neutral and natural for general use.

The stress is:

• реа́льность
• оказа́лась
• сложне́е

So the full sentence is pronounced roughly:

• реа́льность оказа́лась сложне́е

A learner should especially notice:

• the stress in оказа́лась is on -за-
• the stress in сложне́е is on the final -е́-

Yes, often you can.

Depending on context, good English versions include:

• turned out to be
• proved to be
• ended up being

The most neutral and common choice is usually turned out to be.

So Реальность оказалась сложнее is very naturally understood as Reality turned out to be more complex.