You can schedule publish date, not time and not unpublish.Custom crons jobs (schedule anything) will be supported in Elxis 4.3.
Yes, you are right, Flex needs installation. You did it correctly. The update is supposed to occur on a running site. So changing the template to Flex is not usually what people do. But I will change the database update script in order to install Flex too for those want to switch template. Thanks for the report.