The app searches your Google Drive for all sheets with “whendidiwork@” in their name. Nothing will show up if they have been trashed or if no sheets with this name have been created yet.
Well, it depends on your reason. If you no longer want the sheet even in your Goggle Drive, just delete it. If you on the other hand have finished the job or project, or want to start a new sheet for a new month or year, etc., just rename the sheet you want to hide from the app. As long as the name doesn't contain “whendidiwork@” it won't appear in the list.
Not if you don't want to. I personally track all of my times on one calendar named whendidiwork, and then separate different jobs or activities onto their own spreadsheets.
When a calendar is selected, all currently recorded events from one week past, until one week future are displayed.
Only events created through the app are able to be edited or deleted. Any events created directly on the calendar itself cannot be modified through the whendidiwork app.
No problem! Just follow this link to Google Account Permissions, select the whendidiwork application and press revoke.