Hey there! :) Thanks for sticking around and your kind words!
So the 2017 demo which you played contained Chapter 1 and a tiny preview of Chapter 2, the first few minutes.
Part 1 releasing on July 1st contains the whole of Chapter 1 and 2 which will take the story way past the 2017 demo content. But it will end on a cliffhanger as Part 2 will contain Chapter 3, the last third of the story.