Is there anybody can explain that how to use ionicModal methods like initialize(options), isShown() described on doc.
The initialize method is the constructor used internally. That bit is basically showing you the methods you can pass here to the fromTemplate and fromTemplateUrl methods on the $iconicModal service.
The other methods like isShown are to be used on the instance of the modal.
$ionicModal.fromTemplateUrl('my-modal.html', { <- this hash goes to initialize
scope: $scope,
animation: 'slide-in-up'
}).then(function(modal) {
$scope.modal = modal; <- this is the instance to call "isShown"/etc on
});