I am stuck on this last point. Can someone have a look and give me a hint.
1. The <img> element should responsively resize, relative to the width of its parent element, without exceeding its original size.
Code please. Also I have looked at your Java Processing using Processing repl and can suggest a correction. The file that holds the Processing code normally uses pde rather than java as a file extension, so index.pde instead of index.java.