Okay what if hypothetically that single celled organisms is God if we define God as one who created multi-cellular life ...
In the first place, we
don't define God that way.
In the second place, "created" is rather a strange word to describe the relationship between single-celled and multicellular organisms.
Would you say that I was "created" by my great-grandparents? If so, and we define God as "one who created a man", does that mean that my great-grandparents are God.
... could science back this up with scientific facts as they learn more about single celled organisms?
We can watch the evolution of colonial organisms from single-celled organisms, if that's what you mean.