Why is 「～といわず」 the correct expression in this sentence?

Question

The following question is taken from a JLPT N1 grammar/expressions prep book:

彼女はよほど花が好きらしい。家の（　　）花でいっぱいだ。

１　中といわず外といわず　　　　２　中といっても外といっても

３　中はともかく外も　　　　　　４　中外もかまわず

In the book, no. 1 is listed as the correct answer, but no explanation is given. I've asked my Japanese teacher why, but she was equally puzzled. To me it seems nos. 1, 2 and 4 are all equivalent or have the same meaning.

Answer 1

First, AといわずBといわず is a set expression, "whether A or B", "no matter it's A or B", "both A and B", etc. See Learn JLPT N1 Grammar: といわず (to iwazu) and ～といわず～といわず（JLPT N1 Grammar）.

• No. 2 almost looks like gibberish to me... What is this といっても supposed to mean?
• No. 3 is grammatically fine, but 家の中はともかく admits it's natural for an ordinary person to have many flowers in a house. The sentence is saying something like "Having many flowers inside a house is understandable, but she even has many flowers outside!"
• No. 4 is also grammatically fine, but this も ("even") feels too strong, "even without worrying..." or "even without regard for...". 構う ("concern", "worry", "bother"...) also feels slightly inappropriate. The sentence would sound like she is an inconsiderate person who does not pay attention to where to place flowers.

You can also say 家の内外(を)問わず花でいっぱいだ, although this may be a bit too stiff.