Регламент выступления уже изменили.

Russian often leaves out the subject when it is unknown, unimportant, or meant in a general they sense.

Here, изменили is 3rd person plural past and can mean something like:

• they changed
• someone changed
• it has been changed in a less formal, more natural way

So the sentence does not necessarily mean that a specific group of people is being talked about. It is a very common Russian way to say that an action was done by unspecified people.

Because this is the common Russian indefinite-personal construction.

The verb is in the plural past form:

• изменил = he changed
• изменила = she changed
• изменило = it changed
• изменили = they changed

In sentences like this, Russian uses the plural form without stating who they are. English often translates this as:

• They already changed...
• Someone already changed...
• ...has already been changed

Регламент can be tricky because it does not always match one single English word.

Depending on context, it can mean:

• regulations
• rules
• procedure
• schedule
• format
• time limit / speaking time rules

In the phrase регламент выступления, it often refers to the rules or allotted time for a speech/presentation, not necessarily a formal legal regulation in the English sense.

So in context, it may mean something like:

• the speaking time limit
• the format/rules for the presentation
• the procedure for the speech

Because выступления depends on регламент and means of the speech/presentation.

So:

• регламент = regulations / format / time limit
• выступления = of the presentation / speech

This is a very common Russian noun + noun pattern, where the second noun goes into the genitive:

• план урока = plan of the lesson
• начало встречи = beginning of the meeting
• регламент выступления = regulations / timing / format of the presentation

The dictionary form is выступление, and the genitive singular is выступления.

Because регламент is an inanimate masculine noun, and in the singular its nominative and accusative forms are the same.

So:

• nominative: регламент
• accusative: регламент

In this sentence, регламент is the direct object of изменили, but its form does not change.

Compare that with a feminine noun:

• программа → accusative программу

If the sentence used программа, the object ending would be more obvious.

Уже means already.

It shows that the action happened before now, often with the nuance that this is earlier than expected, or that the result is now in place.

So the sentence suggests:

• the change has already been made
• this matter is no longer pending

Russian уже is used very much like English already.

Russian word order is flexible, and different orders change the emphasis more than the basic meaning.

This order is neutral and natural:

• Регламент выступления уже изменили.

Possible alternatives:

• Уже изменили регламент выступления.
  Emphasis a bit more on the fact that the change has already happened.

• Регламент уже изменили.
  Shorter, if выступления is understood from context.

• Изменили уже регламент выступления.
  Possible, but more marked and context-dependent.

Russian often puts known information earlier and new or emphasized information later, but there is no single fixed order like in English.

Изменили is perfective.

Its infinitive is изменить.

Perfective aspect means the action is viewed as completed:

• изменили = changed, completed the change

The imperfective partner is меняли or изменяли, which would focus more on process, repetition, or background:

• Регламент выступления уже меняли. = They have already changed the speaking format before / They already used to change it / It was changed already at some earlier point, with more focus on the fact of experience or process depending on context.

In your sentence, изменили tells us that the result is now achieved.

In Russian, the past tense is formed without a separate verb like did or have.

So:

• изменили by itself already means changed

Russian does not need an extra word for:

• they changed
• have changed

Which English translation fits best depends on context.

That is why one Russian past-tense form can correspond to different English past forms.

Yes, very often.

Even though the Russian sentence is structurally active-looking (they changed), the missing subject makes it close in meaning to an English passive.

Possible translations include:

• They already changed the speaking regulations.
• Someone already changed the presentation format.
• The time limit for the speech has already been changed.

English often prefers the passive if the doer is unknown or unimportant. Russian often prefers this plural verb with no subject instead.

Yes. For example:

• Регламент выступления уже изменён.
• Регламент выступления уже был изменён.

These are more explicitly passive and usually sound:

• more formal
• more written
• sometimes more bureaucratic

By contrast, Регламент выступления уже изменили is very natural in everyday Russian and often sounds less stiff.

So both are possible, but the original sentence is the more conversationally common choice.

It can mean several things depending on context.

Выступление can be:

• a speech
• a presentation
• a public appearance
• a performance
• even a musical performance or competitive appearance

So регламент выступления could refer to:

• a conference talk
• a formal speech
• a student's presentation
• a performer’s allotted stage time

You decide the most natural English wording from the situation, not from the Russian word alone.

Russian past tense does not make the same distinction that English does.

So изменили can be translated as:

• changed
• have changed

Choose based on normal English usage in context.

For example:

• If you are simply reporting an event: They changed the format already.
• If you are focusing on the current result: The format has already been changed.

Because the sentence contains уже and a completed perfective verb, English very often prefers has already been changed or have already changed.