2 and 3 will update database fields according to package requirements. It will insert the following fields (if they are not already present): username, activated, activation_code, reset_password_code. Also if activated field is just created, it will set all the current users as activated.
$pass_data is array, which must have old_password, new_password and password_confirmation.
This function search for user with id = $user_id, checks if $pass_data['old_password'] is correct, checks if $pass_data['new_password'] and $pass_data['password_confirmation'] match and saves new password if everything is ok.
It will return array('success' => false, 'message' => '...') in case of fail and array('success' => true) in case of success.