1. Variables are immutable
  2. Number in a mutable variable
  3. Literal strings in variables are immutable
  4. Literal string in a mutable variable can be replaced
  5. A literal string cannot be changed
  6. Really mutable string
  7. Cannot change variable type
  8. Redeclare immutable variable - Shadowing
  9. Redeclare immutable variable and change type - Shadowing