I can answer the 2nd part of your question. You can add a task event trigger to your task. This then will not start this task until the other task in the trigger is either successful or failed.
I don't believe that there is a notification ability in Qlik Sense at this time.
I do think that I saw something at Qlik Branch that someone developed to do this. But I never tried it.
You can always set up and use SMTPAppender. I was able to configure it and it works. I have it configured to sent emails on failures only. I'm sure you could configure it for any event.
You can fin the documentation in Qlik help.
Also, here is a link to a post that describes how to set it up.
Re: Alerts in Qlik Sense
Hope this helps.
You can also use the Notification Connector, which is one of the free Connectors supplied with the Qlik Web Connectors