I'm confused because from my understanding, ありません means "does not have/exist"
- I only have this software. (or I have only this software.)
- I don't have any software but this one.
I know that sentece 2 and 3 have a same meaning in English, and we call 1 an affirmative sentence and 2 a negative sentence.
The given sentece 1 is written in a negative sentence, so you got confused.
If you want to rewrite 1 into an affirmative sentence, it would become like:
4.2 is more commonly used than 4.1
You can use 1 and 4.2 safely, and I prefer 1 to 4.2 for the meaning of 2 or 3.
To clarify, the line I posted was from another person who commented on the artist's/seller's book announcement post. I edited my original post to reflect this.
OP edited the original post according to my answer, so I'll delete all the following answer.
>The context is an artist announced that he is releasing a book about painting digital backgrounds...
If your explanation is correct, don't you think the following sentence is illogical, because the seller says "I'll buy it"?
If I read it logically, it may imply by supplementing the omitted part like:
>背景とかってどうやって描いてるのかすごく気になってたので もしあなたが私なら 絶対買います！
I'm very interested about how backgrounds are painted so, if I were you, I'm definitely buying (the book).