Новая грамматическая тема: конструкция «если не ..., то ...» помогает предложить запасной вариант.

It presents a fallback or second option.

The idea is:

• first option: если не ...
• backup option: то ...

So the speaker is not just naming two alternatives at random. They are saying something like:

• if not X, then Y
• if X doesn’t work, Y
• if not this, then that

Examples:

• Если не сегодня, то завтра.
• Если не чай, то кофе.
• Если не ты, то я.

In all of these, the second part is the reserve choice.

Not quite.

A normal если sentence is a regular condition-result sentence:

• Если пойдёт дождь, мы останемся дома.
  This means: if it rains, we will stay home.

But если не ..., то ... often works more like a contrast between two options:

• Если не сегодня, то завтра.
• Если не он, то она.

So instead of a full cause-and-result meaning, it often gives a replacement option.

Because the first option is being negated.

In other words:

• если не X = if not X
• то Y = then Y

So in:

• Если не автобус, то метро

the meaning is: if not the bus, then the metro.

The не belongs to the first alternative, not to the whole sentence.

For learners, it is best to think of то as the normal and expected partner here.

The standard pattern is:

• Если не А, то Б

Russian speakers may sometimes leave things out in casual speech, but то makes the contrast clear and is the form you should learn first.

So yes: in this textbook-style structure, keep то.

Many different things can go there.

You can use:

• nouns:
  Если не чай, то кофе.
• pronouns:
  Если не он, то она.
• adverbs of time:
  Если не сегодня, то завтра.
• whole clauses:
  Если не получится позвонить, то напишу.

So the pattern is flexible. The grammar of each part depends on what role that word or phrase has in the sentence.

Because если introduces a subordinate part, and Russian normally separates it with a comma.

So the standard punctuation is:

• Если не А, то Б

Even when the sentence is short, the comma is still normally written:

• Если не сейчас, то позже.
• Если не дома, то на работе.

This comma is standard Russian punctuation.

Yes, very often.

Russian is comfortable leaving out a verb when it is easy to understand from context.

For example:

• Если не сегодня, то завтра.
• Если не чай, то кофе.

These are complete and natural in Russian, even though English often feels like it needs extra words such as we’ll do it or I’ll have.

So this pattern is often short and compact.

Или just gives alternatives in a neutral way:

• чай или кофе = tea or coffee

But если не ..., то ... adds a stronger sense of backup or second choice:

• Если не чай, то кофе

This suggests that tea was considered first, and coffee is the substitute.

So:

• или = either/or, neutral list of choices
• если не ..., то ... = if not this one, then that one instead

Yes. This is important.

Sometimes если не is just the ordinary combination if + not, not the special fallback pattern.

Compare:

• Если не знаешь, спроси.
  Ordinary meaning: if you do not know, ask.

• Если не ты, то кто?
  Contrast between options: if not you, then who?

The clue is whether the sentence sets up two alternatives, especially with то.

Because after помогает, Russian often uses an infinitive to say what something helps you do.

For example:

• помогает понять
• помогает запомнить
• помогает объяснить
• помогает предложить

So помогает предложить запасной вариант means that this construction helps someone offer a backup option.

Here предложить is perfective, and that fits the idea of making one complete suggestion.

• предложить = to offer, to suggest once / as a completed act
• предлагать = to be offering / to offer repeatedly or in a more general ongoing sense

In this sentence, the grammar pattern helps you perform a specific act: to offer an alternative. That is why предложить sounds natural.

Because it is the direct object of предложить.

You ask:

• предложить что? — запасной вариант

That means it is in the accusative case.

However, вариант is an inanimate masculine noun, so in the singular its accusative form looks the same as the nominative:

• nominative: запасной вариант
• accusative: запасной вариант

So the form does not visibly change here.

The colon introduces an explanation or a naming of what follows.

So:

• Новая грамматическая тема: ...

means something like:

• New grammar topic: ...

The part after the colon tells you what the new topic is, namely the construction если не ..., то ....