Answer 1

Sweet lord. That's not what I'm talking about. x is a string, right? String is a primitive datatype, so it cannot have properties (such as y). It doesn't matter what datatype would y be, strings still cannot have properties

Answer 2

Because you are trying to access a property of an object that isn't in object format. Try something like this:
Var x = {};
X.norm = "hello";
X.y = 8865;

Answer 3

It's because primitive datatypes cannot have properties. Adding a property to it doesn't magically make it an object, because then what do you do with the initial value?

Answer 4

String: primitive (simple)
Object: not primitive (not simple)

Object: has properties
String: doesn't have properties

Can't add properties to strings, because it's primitive (not object)