Заявитель сравнил личные данные и паспортные данные.

Заявитель means applicant or person submitting an application/request.

It is fairly common in:

• legal language
• government forms
• administrative contexts
• immigration, banking, insurance, etc.

It sounds more formal than an everyday word like человек (person) or клиент (client).

In this sentence, заявитель is the subject: the applicant is the one doing the action.

Russian past-tense verbs agree with the subject in gender and number.

Here the subject is заявитель, which is a masculine singular noun, so the verb is сравнил.

Compare:

• заявитель сравнил = the male applicant compared
• заявительница сравнила = the female applicant compared
• заявители сравнили = the applicants compared

If the real person is female, Russian often still uses заявитель in formal bureaucratic style, but in ordinary language you may also see заявительница.

Сравнил is:

• past tense
• masculine singular
• from the verb сравнить
• perfective aspect

So it means something like compared in the sense of a completed action.

The idea is that the applicant finished comparing the two sets of data.

Russian uses aspect to show how an action is viewed.

• сравнить → perfective → to compare, to finish comparing
• сравнивать → imperfective → to compare, to be comparing, to compare repeatedly/habitually

So:

• Заявитель сравнил личные данные и паспортные данные.
  = The applicant compared the personal data and the passport data.
  This presents the action as completed.

• Заявитель сравнивал личные данные и паспортные данные.
  = The applicant was comparing / used to compare the personal data and the passport data.
  This focuses on the process, duration, or repeated action.

In a simple report of a completed step, perfective сравнил is the most natural choice.

They are direct objects, so they are in the accusative case. But here the accusative looks exactly like the nominative.

Why? Because:

• данные is an inanimate plural noun
• for inanimate plural nouns, accusative = nominative

So:

• nominative: личные данные
• accusative: личные данные

And the same for:

• nominative: паспортные данные
• accusative: паспортные данные

That is why the form does not visibly change.

In this meaning, данные means data/details/information entries, and in Russian it is very commonly used in the plural.

So phrases like these are normal:

• личные данные = personal data
• паспортные данные = passport data/details
• контактные данные = contact details

A singular form данное exists, but it usually means datum or piece of information, and it is much less natural in this kind of administrative phrase.

So for official information fields, Russian strongly prefers the plural данные.

They overlap, but they are not exactly the same.

• личные данные = personal data
  This is a broader category. It can include name, date of birth, address, phone number, and other personal information.

• паспортные данные = passport details/data
  This refers specifically to information from the passport, such as passport series/number, issuing authority, date of issue, etc.

So the sentence suggests that the applicant compared:

1. general personal information, and
2. the passport information

This could mean checking whether they match.

Russian often uses сравнить with two direct objects and no preposition:

• сравнить A и B = compare A and B

That is exactly what is happening here:

• сравнил личные данные и паспортные данные

Russian can also use сравнить A с B:

• сравнить личные данные с паспортными данными

Both are possible, but they are structured differently:

• A и B = compare A and B
• A с B = compare A with B

Your sentence uses the first pattern.

Yes, absolutely. That version is grammatical and natural.

The difference is mostly structural:

• сравнил личные данные и паспортные данные
  = compared the personal data and the passport data

• сравнил личные данные с паспортными данными
  = compared the personal data with the passport data

The second version makes the comparison relationship slightly more explicit, similar to English with.

Both are correct. The original sentence is just a bit more compact.

Because they must agree with данные, which is plural.

In Russian, adjectives agree with the noun in:

• gender
• number
• case

Since данные is plural, the adjectives are also plural:

• личные данные
• паспортные данные

If the noun were singular, the adjective would change too.

Yes. Russian word order is more flexible than English, although the neutral order here is very natural:

• Заявитель сравнил личные данные и паспортные данные.

Other orders are possible, for example:

• Личные данные и паспортные данные сравнил заявитель.
• Заявитель личные данные и паспортные данные сравнил.

But these usually add emphasis, contrast, or a more marked style.

For a neutral statement, the original order is best:

• subject → verb → objects

A natural stress pattern is:

Заяви́тель сравни́л ли́чные да́нные и па́спортные да́нные.

Helpful notes:

• заяви́тель → stress on и
• сравни́л → stress on и
• ли́чные → stress on the first syllable
• да́нные → stress on the first syllable
• па́спортные → stress on па́с-

A rough pronunciation guide:

• zaya-VEE-tyel srav-NEEL LEECH-ny-ye DAN-ny-ye ee PAS-part-ny-ye DAN-ny-ye

It is natural, but it sounds somewhat formal/administrative because of the vocabulary:

• заявитель
• личные данные
• паспортные данные

This is exactly the kind of sentence you might see in:

• official instructions
• application processing notes
• compliance checks
• legal or administrative documents

In everyday speech, a person might say something simpler depending on context, but as an official-style sentence, it sounds perfectly normal.