Why can I assign a new value to a reference, and how can I make a reference refer to something else?

• a) It cannot, the line you quote doesn’t change the reference q, it changes p.
• b) No the literal is constant, but p is a pointer which points at a literal.
  The pointer can be changed, what is being pointed to cannot.
  q = "world"; makes the pointer p point to something else.

You seem to think that this code

int i;
int &j = i;
int k;
j = k;

is reassigning a reference, but it isn’t.
It’s assigning the value of k to i, j still refers to i.
I would guess that this is your major misunderstanding.