Word order in a comparative sentence

Question

The original sentence was interrogative and used「AはBよりC」construction in it

九州では東京よりさくらが早くさきますか。

I could have written something, using simpler constructions but I decided to use the construction with 「同じ」, and faced some troubles.

First off, I didn't know where to put 「さくら」 and 「早く」. I've tried some variants but decided to write it this way since it looked to me like the most correct one:

いいえ、東京ではさくらが九州と同じ早くさきます。

Edited: いいえ、東京ではさくらは九州と同じくらい早くさきます。

Others are:

東京と九州と同じさくらが早くさきます。

東京と九州とさくらが同じ早くさきます。

and I believe that they are incorrect.

Second off, I wonder if I can change the topic of the sentence by replacing one city with another. What I wanted to do is to put some kind of an emphasis on the fact that Tokyo's sakura blossom does not differ from Kyushu's and starts at almost the same time. Was it successful? And can I actually do so? Can I change the topic of the answer from 「九州」 to 「東京」even though the topic of the question is 「九州」?

Also, I'd like to know the function of 「で」 here. I know that 「noun + で + verb」 means, that the noun is the place where an action is/was taking place, but I'm not sure about it when it's combined with は. Does it mean that the place of action IS THE TOPIC and does it put emphasis on this very place?

P.S. I understand that Kyushu's sakura blossom is more likely to happen earlier because the island lies to the south of Japan, whereas Tokyo is almost in the middle, but what if we imagine that it's possible? Can I answer the question by replacing 「九州」 with 「東京」, making 「東京」be in the first place?

Answer 1

The original sentence was interrogative and used「AはBよりC」construction in it
九州では東京よりさくらが早くさきますか。
I could have written something, using simpler constructions but I decided to use the construction with 「同じ」

In that case I think it'd be natural to respond using 「同じころに」("at around the same time"), not 「同じくらい早く」("as early as"), like this:

「いいえ、九州では(orでも)、東京と同じころに桜が咲きます。」
「いいえ、九州では(orでも)、桜は東京と同じころに咲きます。」
or just: 「いいえ、（九州と東京とでは、桜は）同じころに咲きます。」

_{Depending on the context, you could respond like 「九州では、東京と同じくらい早く桜が咲きます。」/「九州でも、桜は東京と同じくらい早く咲きます。」, but these would imply that Kyushu and Tokyo's sakura starts earlier than other places, rather than just saying Kyushu's sakura and Tokyo's sakura start at the same time.}

「九州と同じ早く咲きます」 is grammatically incorrect, since 「同じ」("same") can modify a noun (eg. ◎「同じ人」"the same person" ◎「同じころ」"the same time" ◎「同じくらい」"the same degree") but not an adjective, adverb or verb (eg. ×「同じ大きい」×「同じ早い/早く」×「同じ咲きます」). 「同じさくら」 would mean "the same (kind of) sakura".

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Second off, I wonder if I can change the topic of the sentence by replacing one city with another. What I wanted to do is to put some kind of an emphasis on the fact that Tokyo's sakura blossom does not differ from Kyushu's and starts at almost the same time. Was it successful? And can I actually do so? Can I change the topic of the answer from 「九州」 to 「東京」even though the topic of the question is 「九州」?

It's not natural to reply 「東京では、九州と同じ...」 to the question 「九州では東京より...？」. To start the answer with 東京, I can think of a response using 「～のほうが」 , but the meaning should be different:

「いいえ、東京のほうが（九州より桜が）早く咲きます。」

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Also, I'd like to know the function of 「で」 here. I know that 「noun + で + verb」 means, that the noun is the place where an action is/was taking place, but I'm not sure about it when it's combined with は. Does it mean that the place of action IS THE TOPIC and does it put emphasis on this very place?

The は in a sentence that starts with 「[Place]では、～～」 can be the topic particle (i.e. the place of an action is the topic), as well as the contrastive particle. Whether an emphasis is put on the place or not would depend on the context.