Both arguments are optional. The options argument should be an object containing the desired settings. The element argument is the element to apply it to, which is by default the body element.
step represents the the number of iterations that are skipped across the rgb spectrum
delay represents the time in milliseconds between each iteration
amazing.stop(); // does what it says on the tin amazing.start(i); // i is optional - start at iteration i or resume
No, not at all.