Since missing parameters are assigned as 'Undefined' would that cause 'Null' to be output if trying to document.write() the undefined parameter?

Answer 1

it would cause undefined, the value of an undefined variable is undefined. In JS:

null === undefined; // returns false

//Note I used === and not ==.
null == undefined; //will return true.

Answer 2

The short answer is no. False, Undefined, NaN, Null, "", and 0 are all different values of nothing.

Answer 3

the function would not execute