Стойка для микрофона находится на сцене.

Because стойка is the subject of the sentence: it is the thing being talked about. In dictionary form, that is nominative singular.

• стойка = stand
• It is feminine, singular, nominative.

So the sentence is structured like:

Стойка для микрофона = the microphone stand
находится на сцене = is located on the stage

Because для means for, and it requires the genitive case.

So:

• микрофон = microphone
• after для, it becomes микрофона

That gives:

• стойка для микрофона = a stand for a microphone

This is a very common Russian pattern:

• чашка для чая = a cup for tea
• сумка для книг = a bag for books

Because the preposition для always takes the genitive case.

The noun микрофон is masculine, and its genitive singular form is микрофона.

So:

• nominative: микрофон
• genitive: микрофона

This is not optional here. After для, you must use the genitive.

Yes. Literally, that is exactly what it means.

In natural English, we usually say microphone stand, but Russian often expresses this idea with:

• noun + для + genitive

So Russian says the equivalent of stand for a microphone, while English prefers a compound noun.

Находится means is located, is situated, or simply is in a certain place.

In this sentence, it gives a neutral, slightly formal sense of location:

• Стойка для микрофона находится на сцене.
• The microphone stand is located on the stage.

In everyday English, we often just translate it as is on the stage.

In Russian, you usually need some predicate in a full sentence. In the present tense, Russian often omits to be, but with location it is very common to use a verb like находится, стоит, лежит, and so on.

Compare:

• Стойка для микрофона находится на сцене. = neutral: The microphone stand is located on the stage.
• Стойка для микрофона стоит на сцене. = more physical: The microphone stand is standing on the stage.

You may also hear short, less formal expressions in conversation, but находится makes the sentence complete and standard.

Yes, very often you could.

• находится = neutral location, is located
• стоит = emphasizes upright position, is standing

Since a microphone stand normally stands upright, Стойка для микрофона стоит на сцене sounds very natural too.

The difference is mostly:

• находится focuses on where it is
• стоит focuses on its position as well as location

Because Russian uses на with many places that are thought of as a surface, platform, or area of activity. A stage is one of them.

So:

• на сцене = on the stage

Using в сцене would mean something very different, more like inside the scene, and would usually not fit this context.

Russian often says:

• на столе = on the table
• на улице = in the street / outside
• на сцене = on the stage

Because after на when it means location, Russian uses the prepositional case.

So:

• nominative: сцена
• prepositional: на сцене

This is the regular pattern for many feminine nouns ending in -а:

• комната → в комнате
• школа → в школе
• сцена → на сцене

No, Russian word order is fairly flexible. This sentence has a neutral, standard order:

• Стойка для микрофона находится на сцене.

But other orders are possible, depending on emphasis:

• На сцене находится стойка для микрофона.
  This puts more focus on the stage as the location.

In English, word order is much more rigid, but in Russian changing the order often changes focus rather than basic meaning.

The main word stresses are:

• сто́йка
• микрофо́на
• нахо́дится
• сце́не

So the sentence is pronounced roughly like:

СТОЙ-ka dlya mee-kra-FO-na na-HO-deet-sya na STSE-ne

The exact English-style approximation is imperfect, but the stress placement is important in Russian.

Because Russian has no articles.

So стойка can mean:

• a stand
• the stand

and стойка для микрофона can mean:

• a microphone stand
• the microphone stand

The context tells you which meaning is intended.

Yes. Another common option is:

• микрофонная стойка

This is an adjective + noun structure, literally something like microphone-related stand.

So both can work:

• стойка для микрофона
• микрофонная стойка

The version in your sentence is very clear and transparent for learners because it literally shows the relationship: a stand for a microphone.