kotosi no sakura ha reinen yori hayaku mankai ni natta sou desu.

今年の桜 means the cherry blossoms of this year or more naturally this year's cherry blossoms.

Here, の links two nouns:

• 今年 = this year
• 桜 = cherry blossoms

So A の B often means:

• B of A
• A's B
• B related to A

In this sentence, 今年の桜 is a noun phrase acting as the topic of the sentence.

は marks 今年の桜 as the topic: what the sentence is about.

So the sentence is roughly structured like:

• As for this year's cherry blossoms, ...

Using は suggests the speaker is making a statement about them, often with some contrast or comparison in the background. That fits well here, because the sentence compares this year with 例年 (usual years).

If you used が instead, the nuance would shift more toward identifying or emphasizing the subject rather than setting it up as the topic.

例年 means usual years, an average year, or every year normally.

より means than in comparisons.

So:

• 例年より = than usual
• more literally: than in a typical year

This phrase sets up the comparison:

• 例年より早く = earlier than usual

早い is an い-adjective meaning early.

When an い-adjective modifies a verb, it usually changes from -い to -く:

• 早い → 早く

Here it modifies なった:

• 早くなった = became early / happened earlier

In this sentence, 早く describes the timing of becoming full bloom:

• 満開になった = became full bloom / came into full bloom
• 早く満開になった = came into full bloom early

満開 is a noun meaning full bloom.

With なる, many nouns and na-adjectives take に:

• 静かになる = become quiet
• 春になる = become spring
• 満開になる = come into full bloom / reach full bloom

So に marks the resulting state.

This is a very common pattern:

• Noun / na-adjective + に + なる = to become ...

Yes, literally it is something like become full bloom, but in natural English we usually say:

• come into full bloom
• reach full bloom

So:

• 桜は満開になった = The cherry blossoms came into full bloom

This is a set phrase often used for flowers, especially cherry blossoms.

なった is the past form of なる.

The sentence is reporting that the cherry blossoms already reached full bloom:

• 満開になる = come into full bloom
• 満開になった = came into full bloom / reached full bloom

Even though English sometimes says are in full bloom, Japanese here focuses on the change/event of reaching that state.

Here, そうです is the hearsay use, meaning:

• I hear that ...
• They say that ...
• Apparently ...

So the speaker is not necessarily stating this from direct personal knowledge. They are reporting information they heard from someone else, the news, a weather report, and so on.

So the full sentence has the nuance:

• I heard that this year's cherry blossoms reached full bloom earlier than usual.

Japanese has two very common そう patterns:

1. Hearsay そうです

   • means I hear that ... / they say that ...
   • attaches to plain forms
   • example: 雨が降るそうです = I hear it's going to rain

2. Appearance そう

   • means looks ... / seems ...
   • example: おいしそう = looks delicious
   • example: 雨が降りそうです = It looks like it's about to rain

In your sentence:

• なったそうです

This is hearsay そうです, because it follows the plain past form なった and reports information.

Yes, that is possible, but the nuance changes.

Compare:

• 今年の桜は...

  • this year's cherry blossoms
  • focuses on the cherry blossoms associated with this year

• 今年は桜が...

  • this year, the cherry blossoms...
  • focuses on this year as the time frame

Both can be natural, but they organize the information differently.

Your sentence chooses 今年の桜は, which treats this year's cherry blossoms as one topic unit.

They are similar, but not identical in structure.

• 早く満開になった

  • came into full bloom early
  • more direct and compact

• 満開になるのが早かった

  • literally the becoming-full-bloom was early
  • emphasizes the timing a bit differently

Both can express the same basic idea, but 早く満開になった sounds very natural and straightforward in this sentence.

Here are the main readings:

• 今年 → ことし
• 桜 → さくら
• 例年 → れいねん
• 早く → はやく
• 満開 → まんかい
• なった → なった
• そうです → そうです

So the whole sentence is read:

ことし の さくら は れいねん より はやく まんかい に なった そう です。

Yes. Japanese nouns usually do not mark singular vs. plural the way English does.

So 桜 can mean:

• a cherry tree
• cherry blossoms
• cherry blossoms in general
• the cherry blossoms in a certain place/context

In this sentence, because of 満開になる, 桜 is best understood as the cherry blossoms rather than a single tree.

A useful breakdown is:

• 今年の桜は = as for this year's cherry blossoms
• 例年より = than usual
• 早く = early / earlier
• 満開に = into full bloom
• なった = became / came
• そうです = I hear / apparently

So the pattern is:

[Topic] は [comparison] より [adverb] [state] に なる + そうです

More generally:

• A は B より C く D に なった そうです

This expresses:

• I heard that A became D in a C-er way than B

In natural English here:

• I heard that this year's cherry blossoms came into full bloom earlier than usual.