Hmm. I learned something new. Going by your OP and your post, I'd say
1. any invented story, idea, or concept: His account of the event is pure myth.
Invented stories aren't bad. Many people made up stories or
created stories, I guess better way of saying it to explain events in nature and purpose of society. It doesn't mean the meaning behind the story is false, it just means the story-the people, the place, etc-are created for a purpose.
The Biblical account of the Garden of Eden isn't proven. I think they found the Garden somewhere in Africa; but, that is our attempt to connect the supernatural with a physical place and story. Many religions do it all the time. A specific place, sacred object, etc has specific spiritual significance, relates to the event account in the Bible, and automatically it's true.
It doesn't work that way.
Who can prove that the god "hovered over the sky and create the land and waters." We know they exist. Believers feel that if someone exist it must have a creator. That's the thought connection between
believers and that's fine. However, many stories account for this connection and they are myths many are not facts.
That doesn't discount that the stories aren't valuable. There are many accounts for the creation of the earth. The Bible isn't unique in that regards either. If anything, some religions have more accounts (so more possibility of factual accuracy) then the Bible
It doesn't make the Bible wrong. I wouldn't use false since it's sacred book to others but yes, the stories in the Bible are not real. It is for the message not to be taken literally.
2. an imaginary or fictitious thing or person.
There was a talking donkey in the Bible not to mention the snake. Trees that forever burn. Waters that go as high as the skies. People turning to ashes. Towns dissolving in the sin of fire and smoke.
These are myths (as you defined)
I can't remember the story of the talking donkey, but it had a meaning. I think, like the other stories in the Bible, it warning the biblical character (and those who believe in the Bible) what would happen if they were to do X. The snake isn't a real talking snake and he didn't have legs. Does that matter? No. The story is just telling you how sin came into the world. It's a moral story that attempts to define why we do bad things. A lot of religions have stories that account for suffering and our bad actions. The Bible isn't unique.
3. an unproved or false collective belief that is used to justify a social institution.
First thing that popped in my mind was Catholicism. Yes, there are unproven beliefs in the Bible. Since some stories are imaginary, yes, some
facts of the story are false but the meaning of the belief isn't. You can't prove false something that you can't prove exist to begin with.
That and the Roman government took Christianity and made it its own religion. Roman politics and beliefs mixed in and it was no long a Jewish faith carried on by the Apostles. Christianity is a Jewish teaching engraved in Roman beliefs.
The reformation tried to take a lot of the Romanism out but that's Christianity. However, who
knows what Christ said without writings from Christ himself? You are getting things third and fourth hand. How in the world can anyone consider what's in the Bible accurate and even more so the word of god when the Bible is a leather (etc) book with words on it.
There are a lot of stories, myths (your definition and mine), false things, unproven beliefs, people, and items in the Bible.
A believers focus should not, in my opinion, try to prove the Bible is true or real. If it's not, how does that affect your faith in Christ?
Is your faith in Christ and his existence depended on the Bible or on Christ and his father themselves?
If it's depended on the Bible, where do you place Christ and his father?