Это последний вопрос на сегодня.

In this sentence, это works like this / it is in English:

• Это последний вопрос на сегодня.
• literally: This is the last question for today.

Russian often uses это to identify or present something. In English, we would usually need is, but Russian normally leaves out the present-tense verb to be.

So the structure is roughly:

• Это = this / it
• последний вопрос = the last question
• на сегодня = for today

Because in modern Russian, the verb to be is usually omitted in the present tense.

So:

• Это последний вопрос. = This is the last question.

But in past or future tense, Russian does use forms of to be:

• Это был последний вопрос. = This was the last question.
• Это будет последний вопрос. = This will be the last question.

So the missing is is completely normal.

Good question. Это and этот are related, but they do different jobs.

• это can mean this or this is / it is
• этот means this before a masculine noun

Compare:

• Это вопрос. = This is a question.
• Этот вопрос = this question

So in your sentence:

• Это последний вопрос на сегодня.

это introduces the whole statement: This is...

If you said:

• Этот последний вопрос...

that would not fit the intended structure.

Because they are the predicate noun phrase after это in a present-tense identifying sentence.

The basic structure is:

• Это
  • noun phrase in the nominative

So:

• вопрос is nominative singular
• последний agrees with вопрос, so it is also nominative masculine singular

Forms here:

• последний = masculine singular nominative
• вопрос = masculine singular nominative

This is similar to saying:

• Это мой брат. = This is my brother.
• Это интересная книга. = This is an interesting book.

Because вопрос is a masculine noun.

Russian adjectives must agree with the noun in:

• gender
• number
• case

Since вопрос is:

• masculine
• singular
• nominative

the adjective must also be:

• masculine
• singular
• nominative

So:

• последний вопрос = correct
• последняя вопрос = wrong
• последнее вопрос = wrong

Here последний means last in the sense of final / no more after this.

So:

• Это последний вопрос на сегодня. means something like:
  • This is the last question for today
  • This is the final question today

It usually means there will be no more questions today, not necessarily forever.

На сегодня is a very common Russian expression meaning for today or as of today / for now, today depending on context.

Literally, на often means for / for the time of / up to in expressions like this.

So:

• последний вопрос на сегодня = the last question for today

This phrasing is very natural when talking about:

• plans
• schedules
• lessons
• meetings
• tasks

Other examples:

• Хватит на сегодня. = That’s enough for today.
• Всё на сегодня. = That’s all for today.

Because сегодня is an adverb-like word, and in the fixed expression на сегодня, it does not change form.

Many time expressions in Russian behave in a fairly fixed way. So although learners often expect a case ending after every preposition, some expressions are more idiomatic and just have to be learned as a unit.

So it is best to remember:

• на сегодня = for today
• на завтра = for tomorrow

as common set expressions.

Yes. Russian word order is flexible.

Your sentence:

• Это последний вопрос на сегодня.

is neutral and very natural.

But you could also hear:

• Это на сегодня последний вопрос.
• Последний вопрос на сегодня.

These versions change the emphasis slightly:

• Это последний вопрос на сегодня.
  neutral, standard
• Это на сегодня последний вопрос.
  emphasizes for today
• Последний вопрос на сегодня.
  sounds like an announcement or heading: Last question for today.

So word order can shift, but the original version is probably the best basic pattern to learn.

Yes, sometimes.

You can say:

• Последний вопрос на сегодня.

This sounds like:

• a heading
• a classroom announcement
• a conversational shorthand

But the full sentence:

• Это последний вопрос на сегодня.

is more complete and explicit: This is the last question for today.

So both are possible, but they are not identical in tone.

Not quite. The stress is important:

• вопро́с

The stress is on the second syllable.

Approximate pronunciation:

• va-PROS

Also, unstressed vowels in Russian are often reduced, so the first о does not sound like a strong English o.

A rough pronunciation of the whole sentence is:

• Э́то после́дний вопро́с на сего́дня.

Stress:

• Э́то
• после́дний
• вопро́с
• сего́дня

Usually it is completely normal here.

In standard Russian, последний вопрос is the ordinary way to say the last question.

You may sometimes hear крайний instead of последний in certain colloquial contexts, especially where people avoid saying last for superstitious or professional-culture reasons. But for normal standard Russian, stick with:

• последний вопрос

That is the safest and most natural choice in this sentence.

Yes. Russian has no articles like a or the.

So вопрос can mean:

• a question
• the question

The exact meaning comes from context.

Here, because of последний and the whole situation, English naturally uses the:

• Это последний вопрос на сегодня. = This is the last question for today.

So Russian does not mark definiteness with an article; you infer it from meaning and context.