Translating: The boy likes elephants.

In Duolingo, it shows the answer to be “al ragazzo piacciono gli elefanti”

Why is it al?

Why is it piacciono and not piace?

Thank you if someone can educate me on this format and sequence . Is this how the sentence is structured when using piacere?

He likes toys. I like my boyfriend. We like fruits.

Grazie!!

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@TryingToLearnItalian
It's ok, you probably haven't come across this yet, but don't worry I'll try to make it clear for you!
First of all, your summary of the rule is correct, it is indeed a sort of reverse of the sentence, the "object" of the English sentence becomes the "subject" of the Italian one and the verb conjugates according to this second element.
Now, let's focus on the "subject" of the English version, the person/animal that likes something, namely the indirect object introduced by "a" in the Italian sentence.
This phrase could either consist of a substantive or a pronoun. Let's see both cases.

1) When it is a substantive it's very simple, you just use the general formula:
a + (article, if required) + substantive
- a Marco
- al bambino [ "al" is the contraction of "a + il" ]
- alla nonna [ alla = a + la]
- ai ragazzi

2) When it is a pronoun, there are two possibilities:
- a + pronoun (ex: a me)
- dative pronoun (ex: mi)
Now, there is absolutely no difference in the literal meaning of "a me" and "mi", both mean "to me" in English, but they are used in different cases.

Let's see this with an example:
- I like ice cream
As I've anticipated, there are two possibilities for this translation:
- a me piace il gelato
- mi piace il gelato
Now, the literal meaning of these two sentences is exactly the same, but they don't have the same "power".
"Mi piace il gelato" is the neutral version. You are just stating that you like ice cream, as simple as it is, no further message.
"A me piace il gelato" is instead a bit different. By using the "a + pronoun" you are in fact highlighting the element "I" and you use this construction, for example, when you are pointing out a contrast.
I like ice cream, but someone else doesn't.

"Il mio ragazzo odia la musica classica. A me invece piace molto." (My boyfriend hates classical music. I instead like it very much)
But if there isn't any reason to highlight that information and I just want to share that I like classical music I would say:
"Mi piace molto la musica classica" - neutral meaning

This rule about pronouns and this shift of meaning doesn't concern only the verb "piacere", but it happens whenever you need to use the "a + pronoun" phrase.
Mi hanno detto che... - they told me that... ("dire" requires an indirect object with preposition unlike "tell")
A me hanno detto che... - they told ME that..., (you are distancing yourself from this statement, you are highlighting that it's just what YOU have been told, but maybe the truth is different?)

Here's the list of dative pronouns:
a me = mi
a te = ti
a lui = gli
a lei = le
a noi = ci
a voi = vi
a loro = gli/ loro(more formal)

(There are actually some exceptions to this list, especially when there is a double object (with the verb "dire" for example, but you won't find any of them with the verb "piacere"), but maybe it's better to see it some other time, when you get more familiar with pronouns and their use.)

Anyway if you still have some doubts or you need some further help, don't hesitate to ask! 😊