Subject Verb

I'll add a few more points here:

1) Prepositions are relational words. They show how one thing relates to another:

I majored in English.
The jar is under the desk.
I am a fan of her music.
He sat by the lake.

2) In this case, "once" is a conjunction (similar to "when") and "released" is an adjective. However, together they serve as an adverbial modifier. The album was a hit. When? Once it was released.

3) Generally, subjects precede verbs. For instance, we say "They released the album," not "Released they the album." We can use this to figure out the subject-verb core of any sentence. The subject is generally the first noun that is not part of a modifier. The main verb is the first verb after that noun that is not part of a modifier. In this case, the main subject and verb are "album" and "was." Notice that the intervening verbs--"dream" and dance"--are part of a modifying phrase that begins with "who."

4) Lastly, a small point. Since the modifier "who dreams to dance" is providing essential information about which person we're talking about, there should be no commas around it.

DmitryFarber, I always get confused with this. How do we know which question to ask. For example, why can we not ask: What was once released?

In that case "Once released" would be an adjective (as I believe daagh has also mentioned above). So, I am confused.

There's not a great all-purpose answer to your question, and even 99th percentile test-takers can struggle/disagree when it comes to the interpretation of modifiers. The good news is that we can usually get to the right answer without determining whether the modifier is adverbial! However, in this case we know "Once released" has to be an adverbial modifier because it is describing a condition. The album was a hit once it was released. "Once released" doesn't make sense as an adjective: "The once released album was a hit"? "The album that was once released was a hit"? Compare it to "When I was young, I had long hair." Sure, I am the one who was young in this sentence, but only the word "young" describes me. The modifying phrase as a whole tells us when I had long hair. The same thing here: the album was released, but "once released" describes when the album became a hit. (It's not a very interesting modifier, really. You wouldn't expect the album to become a hit before it was released, would you? )

In any case, the vast majority of initial modifiers (modifiers that begin a sentence) are adverbial. They often seem to be adjectival, because they precede and relate to nouns, but they are usually modifying the following action:

Wanting to impress the judges, Linda added a few extra tricks to her routine.

Here, it certainly seems clear that Linda is the one who wanted to impress the judges, and it would certainly be wrong to say "Wanting to impress her judges, a few tricks made Linda's routine better." However, the modifier is adverbial. It gives the context for why Linda added tricks. My rewritten version is wrong not because "Wanting . . . " has to touch "Linda," but because if we rewrite the sentence to make "a few tricks" the subject, then the verb is wrong, too. Anything that follows "Wanting . . . " will have to describe what the person who was "wanting" was trying to do.

Hello DmitryFarber, just wanted to understand this further. Why would the following be incorrect:

Wanting to impress the judges, a few extra tricks were added by Linda added to her routine.

We can ask the question: Why were a few extra tricks added by Linda added to her routine?

So, Wanting to impress the judges still remains adverbial.

And what about "who" ? it should address person in sentence, and "about a british miner's son is not person? Is about is there at start...
Please correct...

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Hi dish1111, who is modifying (describing) British coal miner's son.