For Components I have "Check-in", "Check-out" and "Undo Check-out" options GRAYED OUT. In what scenario, we will have all three options grayed out or disabled? What needs to be done to Check-out the Component for update?
In order to check-in/out a Component (or any other item) you need to be be in the proper Publication. The check-in/out can be performed only in the parent Publication, Primary Blueprint Parent if the item is not localized, or the nearest localized parent (first image). You have this information in the
From Publication column in the list view.
If the item is in workflow, you won't be able to check-in/out the item even from the owning publication until the Workflow Process finishes (second image).
There are some other conditions, but the above situation is the most common. (For example, you cannot check-in an item with a non admin user that was checked-out by an admin or another user, etc.)
See both cases below: