Advanced level of HTML DOM

This project is not completed yet, I upload this project so I can see other people code to learn and complete my project, There are some questions whose answer I couldn't find online, like after created a clone element, then how to access child element of this clone element,

And 2nd question is : I create a button and as user click on this button new p element is created using Javascript but I need to assign new id to each new element, and I want to know that how to write a function so id got created automatically for every new p element.