When you complete a repeating task, it will assign the new due date not immediately, but within an hour after the completion (unless you use “Re-open” option below). Repeating tasks are processed each hour.
Cannot reproduce this :(. In my case it shows completed repeating task with due “today”.
That’s by design. Daily repeating due tasks started today have the first due date for tomorrow. If you want to have first due today, just mark the task with ‘td’.