akaunto no hukkyuu ni bakkuappukoodo wo tukau.

の links two nouns.

So アカウントの復旧 literally means recovery of an account or more naturally account recovery.

• アカウント = account
• 復旧 = recovery / restoration
• アカウントの復旧 = account recovery

In English, we often put the first noun directly before the second noun, but Japanese usually connects them with の.

Here, に marks the purpose or intended use.

So:

• アカウントの復旧に = for account recovery
• バックアップコードを使う = use a backup code

Together:

• アカウントの復旧にバックアップコードを使う
• Use a backup code for account recovery

A useful pattern is:

• N に 使う = use something for N

Example:

• 勉強に辞書を使う。 = Use a dictionary for studying.

So this に is not marking a location here. It is closer to for.

を marks the direct object of the verb.

The verb is 使う = to use, so the thing being used gets を.

• バックアップコードを使う = use a backup code

This is very common:

• ペンを使う = use a pen
• スマホを使う = use a smartphone
• 鍵を使う = use a key

Because Japanese sentences normally place the main verb at the end.

So even though English says:

• Use a backup code for account recovery

Japanese builds it more like:

• For account recovery, a backup code use

That sounds strange in English, but it is normal in Japanese.

This is one of the biggest word-order differences between English and Japanese.

使う is the plain form. It can be used in several situations:

• a neutral statement
• a heading or instruction
• casual/plain writing
• UI or manual-style wording

In a full polite sentence, you might see:

• アカウントの復旧にバックアップコードを使います。

But in menus, help pages, setup steps, or short instructional text, plain form is very common.

So this sentence may feel a bit like a label or brief instruction rather than a full conversational sentence.

Yes. Japanese often leaves out the subject when it is obvious from context.

This sentence does not explicitly say:

• I use
• you use
• one uses

Depending on context, it could mean:

• Use a backup code for account recovery.
• You use a backup code for account recovery.
• We use a backup code for account recovery.

In app or website instructions, the understood subject is often you.

Katakana is commonly used for loanwords, especially words borrowed from English.

So:

• アカウント = account
• バックアップコード = backup code

These are technology-related borrowed terms, so katakana is natural.

By contrast:

• 復旧 is a Japanese word written in kanji
• 使う is a common Japanese verb, written with kanji + hiragana

This mix is very normal in modern Japanese, especially in tech-related language.

復旧 means recovery, restoration, or bringing something back to working condition.

In this sentence, it refers to restoring access to the account, so account recovery is a very natural translation.

It is a somewhat formal or technical word, which fits the context of accounts, systems, and security.

Yes, a very literal translation could sound like:

• use a backup code in account recovery

But in natural English, for account recovery is usually better.

That is because the に here expresses purpose more than location or timing. So for communicates the meaning more smoothly.

You are right: normal Japanese usually does not use spaces like this.

The standard writing would be:

• アカウントの復旧にバックアップコードを使う。

Spaces are often added in teaching materials, language-learning contexts, or sometimes UI text to make the structure easier to see.

So the spaces here are probably just for readability, not part of standard spelling.

Yes, grammatically it can, because Japanese often leaves the subject unstated.

However, in many real contexts, especially app or website instructions, the most natural interpretation is:

• Use a backup code for account recovery.

So the exact English wording depends on context, but the grammar allows more than one subject interpretation.

Yes. The pattern is very useful:

• N に X を 使う = use X for N

Examples:

• 料理に زيت? No, better Japanese example:
• 料理に包丁を使う。 = Use a kitchen knife for cooking.
• 勉強にアプリを使う。 = Use an app for studying.
• 確認にメールを使う。 = Use email for confirmation.

So this sentence is a good model for expressing what something is used for.