How to send tasks to background with progressIndicator?

Hi, there are two questions for me, thanks for your reply.

1. I'm using a ConditionalModal Task like below, but when I pressed the 'Minimize' button, nothing happened and the UI was frozen until this task finished. 

new Task.ConditionalModal(project, "Test Backgroundable", true, PerformInBackgroundOption.DEAF) {
    public void run(@NotNull ProgressIndicator progressIndicator) {
        progressIndicator.setIndeterminate(false);
        for (int i = 0; i < 10; i++) {
            progressIndicator.setText("Testing: " + i);
            progressIndicator.setFraction((i + 1) / 10d);
            try {
                Thread.sleep(1000);
            } catch (Exception e) {
            }
        }
    }
}.queue();

Please tell me how I could send task to background with progressIndicator (just like PerformInBackgroundOption.ALWAYS_BACKGROUND) when I pressed the Minimize button?

It should looks like below (when pressed the Minimize button):

2. I'm using 'Messages.showYesNoDialog' (or any other methods in Messages) to create a dialog, but it seems only the last dialog could remain if two or more dialogs were created. Is there any way to create more dialogs?