Answer 1

what do you mean about 'define'? Ofcourse if you dont initialize them the will be null. You can do this for example:
enum enm{
var1(2),
vae2("hello")
}
here the memmbers are initialized.
but look at this:
enum enm{
var1,
var2
}
now var1 and var2 are null. Sometimes if you using them you will get an error. You can initialize them after creating the enum:
enm.var1 = 2;
enm.var2 = "hello";