You use the example in a way that is not scientificly correct.
Jee... when will you finally get it?
You just assume that if an E.coli can't evolve, then nothing can! And that assumptions is not based on facts...
The common ancestor of fish and mammals could be some fishlike thing yes. It is ridiculous to say that it was a haring or a salmon or whatever fish now around.
The answer on the number of generations is an answer you don't know. I don't know it either. Perhaps we will once know it, but not today.
And to IAMFREE, water cannot reproduce so therefore there can't be generations of water...