Don't compare the Bible to movies, please. I find that rather demeaning.
And no, they do exist as a whole, but they also are written by different people who believe different things. As in... there is no one true voice being written. Just a bunch of smaller voices who may be right.
In a sense, yeah, that's what I believe, but then again, that's actually how it really exists. Because faulty humans wrote it, not God himself.
The reason it evolved a bit, is because the culture did too. One thing to note is that some of the Bible is based upon culture more than universal standards. The universal standards are the Ten Commandments, and most specifically, the respect thing. The whole "homosexuality is a sin"(which isn't state that way anyway) was not meant for everyone to believe.
The reason I don't believe all of it is infallible, is because there's too much stupid stuff that isn't even really written out/abolished later on. Assuming Leviticus meant Homosexuality, it's never abolished later, meaning that we're told that it should be treated as an evil thing. Now, I'm sorry, but I don't care what the Good Book says. I am not about to treat that as anything but an evil idea and that it is just plain wrong. I'm going to cherrypick too. Like we all do.
And I'm going to believe everybody deserves equal rights, including marriage, and that all sexualities are not a sin by any means.(I will note, I'm not a fan of incest, but I do not believe it to be wrong except when genetic problems happen. Outside of that, it's fine)
I preach tolerance to all, equality to all, and the only illegal acts should be the Ten Commandments. I also am fine with Polygamy, to note. Because that is not Adultery as long as they were all married that way.