Стоит мне открыть дверь, как собака сразу бежит в коридор.

No. Here сто́ит is from стоить, not стоять.

• сто́ит = from стоить
• стои́т = from стоять

In this sentence, стоит мне открыть дверь, как... is an idiomatic pattern meaning as soon as I open the door or it only takes me to open the door for...

So стоит here does not mean physical standing. It means something like it only takes or all it takes is.

This is a fixed Russian construction:

стоит + dative + infinitive, как + main clause

It expresses an immediate result:

• Стоит мне открыть дверь, как собака сразу бежит в коридор.
• As soon as I open the door, the dog immediately runs into the hallway.

The idea is:

• one action happens
• another follows right away

It often has a slightly vivid, habitual feel, like whenever this happens, that immediately happens.

Because this construction requires the person involved to be in the dative:

стоит кому? + infinitive

So:

• мне = to me
• тебе = to you
• ему = to him

Examples:

• Стоит тебе позвонить, как он отвечает.
• Стоит нам выйти, как начинается дождь.

In more literal terms, Russian treats this as something like it only takes for me to open the door.

Because открыть is perfective, and here Russian focuses on the single completed trigger action: open the door.

With стоит кому-то + infinitive, the infinitive is very often perfective when the meaning is as soon as someone does X once, Y happens.

• открыть дверь = to open the door
• нажать кнопку = to press the button
• сказать слово = to say a word

Perfective fits well because the opening of the door is the event that triggers the dog’s reaction.

If you used открывать, it would sound less natural here because that would suggest an ongoing or repeated process rather than the moment of opening.

Here the present tense describes a habitual or typical reaction.

So собака сразу бежит в коридор means something like:

• the dog immediately runs into the hallway
• the dog always runs into the hallway right away

Russian often uses the present tense for repeated, regular behavior. The sentence is not mainly about one unique event; it describes what normally happens every time the speaker opens the door.

Because бежит is imperfective and works well for a repeated, general pattern.

• бежит = runs / is running
• побежит = will start running / will run off

In this sentence, the speaker is describing a regular reaction, not one future event. So imperfective present is the natural choice.

If you said побежит, it would sound more like one specific future occasion:

• Стоит мне открыть дверь, как собака сразу побежит в коридор.

That can work in the sense of if I open the door now, the dog will immediately run into the hallway, but it changes the feel from habitual to more one-time/future.

Because the dog is moving into the hallway.

In Russian:

• в + accusative = motion into a place
• в + prepositional = location in a place

So:

• в коридор = into the hallway
• в коридоре = in the hallway

Since бежит involves movement toward a destination, Russian uses в коридор.

No. Here как is part of the pattern ..., как ..., where it introduces the result that follows immediately.

So in this construction:

• Стоит мне открыть дверь, как...

как means something like:

• and immediately
• when suddenly
• and then right away

It is not the question word how here.

Because the sentence has two clauses:

1. Стоит мне открыть дверь
2. как собака сразу бежит в коридор

Russian separates them with a comma. This punctuation is standard in this construction.

Yes, very naturally:

Как только я открываю дверь, собака сразу бежит в коридор.

This is close in meaning. But there is a small difference in feel:

• Стоит мне открыть дверь, как... is more idiomatic and expressive
• it emphasizes how quickly and automatically the second action follows the first

It can feel a bit like the moment I open the door... or no sooner do I open the door than...

So как только is a good paraphrase, but the original has a slightly stronger immediate-result flavor.

сразу means immediately / right away.

The construction already suggests a quick result, so сразу is not strictly necessary. But it reinforces the idea that the dog reacts instantly.

Compare:

• Стоит мне открыть дверь, как собака бежит в коридор.
• Стоит мне открыть дверь, как собака сразу бежит в коридор.

The second one is more explicit: the dog does not hesitate.

Be careful: changing the word order can change the meaning.

• Стоит мне открыть дверь, как... = as soon as I open the door...
• Мне стоит открыть дверь usually means I should open the door or it would be worth my opening the door

So the original order is important because it signals this special idiomatic construction.

Inside the second clause, word order is more flexible:

• как собака сразу бежит в коридор
• как сразу собака бежит в коридор

But the original version sounds the most natural.

Yes, it is common and very useful. Native speakers use it to describe something that happens immediately whenever another thing happens.

Examples:

• Стоит ему начать говорить, как все замолкают.
• Стоит нам выйти из дома, как начинается дождь.
• Стоит ей увидеть кота, как она улыбается.

It is a good pattern to learn because it is natural, expressive, and frequent in both speech and writing.