This is a really tough question. Extinction is when a genetically unique group is no longer in existence. It is more likely, in the way I understand your question that the earliest organism actually evolved into a genetically similar, yet maybe physically different looking organism.

That depends on your definition of "extinction".
The first organism had descendants, these being the other organisms. These new organisms evolved, so that they were different from their ancestor. No organism today is the same as that ancestor, so we could say that it is extinct, or that its form and biochemistry are extinct, because nothing alive today has them. But, all organisms today carry on that ancestor's heritage...

Yes, most organisms that once grew on Earth are now extinct.