Если код подтверждения не придёт, я перезвоню в банк.

This is a normal difference between English and Russian.

In Russian, when you talk about a real future condition, you usually use a future form:

• Если код подтверждения не придёт, я перезвоню в банк.

Russian does not avoid the future after если the way English does. So не придёт is exactly what you expect here.

If you used не приходит, that would sound like a general or repeated situation, something more like if the code doesn't usually come / isn't coming, not this one future case.

Because прийти is a perfective verb, and perfective verbs form the future with a single word:

• приду
• придёшь
• придёт

Perfective here shows one completed event: the code either arrives or it does not.

Будет приходить is an imperfective future and usually suggests an ongoing, repeated, or process-like action, which does not fit a one-time confirmation code very well.

So:

• придёт = will arrive once
• будет приходить = will be coming / will keep coming

Придёт is the 3rd person singular future of прийти.

This verb has a stem change in its future forms:

• прийти = to come, to arrive
• я приду
• ты придёшь
• он/она/оно придёт

So yes, it is a bit irregular-looking. The best way to learn it is as a whole set of forms rather than trying to build it mechanically from the infinitive every time.

Its imperfective partner is приходить.

Подтверждения is genitive singular.

The phrase код подтверждения literally works like code of confirmation. Russian often connects two nouns this way:

• номер телефона = phone number
• чашка чая = cup of tea
• код подтверждения = confirmation code

So the pattern is:

• код = the main noun
• подтверждения = answers код чего? = code of what?

A detail that confuses learners: подтверждения can also look like a plural form in other contexts, but here it is singular genitive.

Because код подтверждения is the standard, natural Russian way to say confirmation code.

If you said подтверждающий код, it would sound more like a code that confirms something, which is not the usual meaning here.

Russian often prefers a noun + genitive construction where English uses a noun as an adjective-like modifier:

• confirmation code → код подтверждения
• bank card → банковская карта or sometimes other patterns, depending on the word
• phone number → номер телефона

So код подтверждения is idiomatic Russian.

Not exactly.

• позвоню = I will call
• перезвоню = I will call back / call again later

The prefix пере- here adds the idea of a repeated or return call.

So in this sentence, я перезвоню в банк suggests that the speaker will make another call to the bank, probably because they were already dealing with the issue and are waiting for the code.

With phone verbs, Russian often uses different patterns depending on what you are calling.

For a person, the dative is common:

• позвонить другу = to call a friend

For an institution, company, office, service, and so on, Russian very often uses в + accusative:

• позвонить в банк
• позвонить в офис
• позвонить в полицию

So перезвоню в банк is the natural way to say I’ll call the bank back.

Even though в банк literally looks like movement into the bank, with phone calls it is just a normal Russian pattern.

Yes.

Если код подтверждения не придёт is a subordinate clause, and я перезвоню в банк is the main clause. Russian separates them with a comma:

• Если код подтверждения не придёт, я перезвоню в банк.

This is standard punctuation.

It is optional.

You can say:

• Если код подтверждения не придёт, я перезвоню в банк.
• Если код подтверждения не придёт, то я перезвоню в банк.

Both are correct.

Adding то can make the structure feel a little more explicit or slightly more emphatic, but the meaning stays the same.

Yes, that is also grammatical.

Compare:

• Если код подтверждения не придёт, я перезвоню в банк.
• Если не придёт код подтверждения, я перезвоню в банк.

The first is a neutral, straightforward order.

The second puts a little more focus on the event not arriving before naming what it is that does not arrive. It can sound slightly more dynamic or context-driven.

Russian word order is flexible, but the original sentence is very natural and neutral.

Yes, Russian could drop it:

• Если код подтверждения не придёт, перезвоню в банк.

That is still correct, because перезвоню already tells you the subject is I.

But including я is also very normal. It can make the sentence a bit clearer, more explicit, or slightly more emphatic. In everyday speech, both versions are possible.

The correct stressed vowel in this form is ё:

• придёт

In many Russian texts, especially informal ones, ё is often written as е:

• придет

But the pronunciation is still the same: придёт.

So if you see придет, you should usually understand it as придёт here.

The main stresses are:

• Е́сли
• подтвержде́ния
• придёт
• перезвоню́
• банк

So a natural pronunciation is:

• Е́сли код подтвержде́ния не придёт, я перезвоню́ в банк.

A few useful stress notes:

• придёт has stress on the last syllable
• перезвоню́ also has stress on the last syllable
• подтвержде́ния has stress on де

Because both actions refer to the future:

1. the code may or may not arrive
2. if it does not, the speaker will call back

Russian expresses both of these as future actions:

• не придёт = will not arrive
• перезвоню = I will call back

Also, both verbs are perfective here, which fits the meaning of single completed events:

• one arrival
• one callback

So the sentence is very compact and natural Russian.