CakePHP 4 : Simple JSON view return

Question

I am new in cakephp, I am trying to develop a simple REST BREAD (BROWSE, READ, EDIT, ADD, DELETE) using cakephp version 4. After installed I created a simple controller called UsersController with method index,view,edit,delete. Not created any model and templates yet.

For Browse json, in Users/index method I have used code like

public function index()
{
          $users = $this->Users->find('all');
          echo json_encode($users);
          exit;
} 

Output :

[
  {
    "id": 1,
    "username": "jone",
    "created": "2020-01-22T00:00:00+00:00",
    "modified": "2020-01-22T00:00:00+00:00"
  }
]

Questions :

1) Without using exit how I will prevent controller to render not found template error exception ?

2) How I will change http response code using cake asset. example 200 ok will be 2000 ok. ?

3) Without use json_encode , am I able to return a json view using cakephp asset, if yes then how ?