Едва зазвонил дверной звонок, как я сразу открыл дверь.

Here едва means hardly, barely, or more naturally in English as soon as in the pattern едва ..., как ....

So the sentence has the sense of:

• Hardly had the doorbell rung when I immediately opened the door
• or more naturally: As soon as the doorbell rang, I immediately opened the door

By itself, едва often means barely or hardly:

• Я едва успел = I barely managed / I hardly made it in time

But in this construction, it introduces something that happens almost immediately before the next action.

In this sentence, как is part of the fixed construction едва ..., как ....

This pattern means:

• hardly ... when ...
• no sooner ... than ...
• as soon as ...

So:

• Едва зазвонил дверной звонок, как я сразу открыл дверь.

literally feels like:

• Hardly did the doorbell start ringing, when I immediately opened the door.

In natural English, we usually would not translate как separately. It is just part of the Russian structure.

They are very close, but not exactly identical in tone.

• Едва ..., как ... sounds a bit more literary or expressive.
• Как только ... is more neutral and very common in everyday speech.

Compare:

• Едва зазвонил дверной звонок, как я сразу открыл дверь.
• Как только зазвонил дверной звонок, я сразу открыл дверь.

Both mean roughly As soon as the doorbell rang, I immediately opened the door.

The first version puts slightly more emphasis on how little time passed between the two actions.

Because зазвонил is perfective and here it means started ringing.

• звонить = to ring / to be ringing / to call
• зазвонить = to begin ringing

In this sentence, the important point is the moment the sound began:

• Едва зазвонил дверной звонок... = As soon as the doorbell started ringing...

If you said звонил, that would describe the process or duration of ringing, not the sudden start. That would sound less natural here, because the sentence is about one action happening immediately after another.

Because it agrees with дверной звонок, which is:

• masculine
• singular

Even though дверной звонок comes after the verb, it is still the subject.

So the structure is:

• зазвонил = rang / started ringing — masculine singular past form
• дверной звонок = the doorbell

Russian often allows the verb to come before the subject, especially in narration.

Russian word order is flexible. Putting the verb first here is natural and helps the sentence sound more dynamic.

• Едва зазвонил дверной звонок...
  means literally something like Hardly had rung the doorbell...

You could also see:

• Едва дверной звонок зазвонил...

but that sounds less natural here.

Verb-first order is common when introducing an event, especially in storytelling:

• Открылась дверь
• Раздался звонок
• Пришёл отец

So this word order is normal and stylistically smooth.

Because открыл is perfective and describes a single completed action.

• открывал = was opening / used to open / opened repeatedly
• открыл = opened, completed the action

In this sentence, the speaker is talking about one quick reaction to the doorbell:

• the bell rang
• I opened the door

So perfective открыл is exactly what Russian normally uses here.

Yes, едва ..., как ... already suggests that the second action happened very quickly after the first.
Сразу adds extra emphasis: immediately, right away.

So the sentence strongly stresses the speed of the reaction:

• Едва зазвонил дверной звонок, как я открыл дверь.
  = As soon as the doorbell rang, I opened the door.

• Едва зазвонил дверной звонок, как я сразу открыл дверь.
  = As soon as the doorbell rang, I opened the door immediately.

It is a bit redundant in a good, natural way: it makes the response sound especially prompt.

Because the sentence has two clauses:

1. Едва зазвонил дверной звонок
2. как я сразу открыл дверь

Russian normally separates such clauses with a comma. In the fixed construction едва ..., как ..., the comma is standard.

Yes, it could be omitted:

• Едва зазвонил дверной звонок, как сразу открыл дверь.

Russian often drops subject pronouns when the subject is clear from the verb ending. Here открыл already shows I if the context makes it clear.

But keeping я is also perfectly natural. It can make the sentence a little clearer or slightly more emphatic:

• ...как я сразу открыл дверь = ...when I immediately opened the door

It is natural Russian, but the pattern едва ..., как ... is a little more literary or narrative than the most neutral everyday option.

In ordinary conversation, many speakers would more likely say:

• Как только зазвонил дверной звонок, я сразу открыл дверь.

The original sentence is still completely understandable and normal, especially in writing or storytelling.

Yes. Дверной звонок means doorbell. Another very common way to express the idea is with a verb like:

• раздался звонок в дверь = there was a ring at the door / the doorbell rang

For example:

• Едва раздался звонок в дверь, как я сразу открыл дверь.

That is also very natural.

So:

• дверной звонок = the physical doorbell
• звонок в дверь = the ringing at the door / the doorbell ring

A fairly literal breakdown is:

• Едва = hardly / as soon as
• зазвонил = started ringing
• дверной звонок = the doorbell
• как = when / than, as part of the pattern
• я = I
• сразу = immediately
• открыл дверь = opened the door

So literally:

• Hardly had the doorbell started ringing when I immediately opened the door.

Natural English:

• As soon as the doorbell rang, I opened the door immediately.