Welcome to the forum, jbacinti.
1) To use the "Daily View" you need to right click -> options... -> skins -> advanced>>>
Open Shadow4 on the left side (available skins), select Daily View and click on the right pointing black arrow. Now you will see the Daily View as a window on the right side (active skins)
2) Events can't be marked as completed, but Tasks yes. If you're using the Task/ToDo list, you can click on the white circle to mark it as completed. Also, in the same Active Skins section as 1), you can change the setting... for ToDo list to hide/show completed, cancelled and future tasks.