As a guide as to which way is towards heaven & which way is towards hell.

Or tail bones?

Christian’s aren’t big thinkers

Well, you are also talking about people depicting a man supposedly born in the Middle East as being an Aryan.
Any semblance of reality is not the point for these clod heads.

Christians aren't big on thinking. I'd suppose that if the artist left out the belly button, the Christian patron woudl isist on there being one, so it would "look right".

Because GODD in all its wisdom, who designed all things perfect, knew perfectly well there would need to be a place for lint.all that other shit came later....next question..

Because science and logical thinking are not in their toolbox

There are also many people who believe that a man has one less rib than a woman.
And they also think that this is how male skeletal remains are distinguished from a female.

The question has been asked before and I forget what apologists use as the standard reply. Of course, there are no pictures of the imaginary parents of all of us to go by.

Keep asking those questions. It's good to make them think.

In the middle ages it was considered a mater of importance, if Adam and Eve had belly buttons. So much so that the theology often changed with the administration, so artists were forced to use fig leaves etc to cover the area, in fear of being charged with a crime if they got it wrong, or a new bishop had different ideas.

When Adam got his rib nicked, had to remove from his body so was born what we know as the belly button. Making Eve, had to shove that rib thro skin so same deal. A hole for ribs.

BTW this is where the term "rib eye" came from, for all the carnivores out there who have laid awake at night contemplating the great mysteries of life.

Mysterious ways and all that

HAH! I once worked for a very high-level man who had a print of SATAN hanging behind his desk. Satan had a naval....I asked this same question and, to my absolute delight, he sat there, mute!

Easy answer SRQ1. Just read the bible. Genesis 14:37 reads "And thusly God gave unto Adam and Eve the button upon their bellies and spoketh the words 'Thine belly buttons are good and bring amusement when poked'".

They are portrayed in artists paintings and are not photographs.

Because the artists probably didn't know from where belly buttons came. The people who commissioned the paintings and did them (usually men) weren't bright enough make the connection between an umbilical cord (which they'd probably never seen before) and a belly button as they usually and traditionally weren't in the room when women were giving birth.

Answer: Man is made in the image of God, and God has a belly button. And why is this you may well ask, to which the answer is that He fucked his own mother before He existed so that He could be born into existence, hence His belly button. That answer tends to annoy the crap out all Christian fundamentalists.

Are you sure they're not just tattoos artfully designed to look like belly buttons?