Can a Windows update be "canceled" after it is "installed" but before it is "updated"?

Solution 1:

A reboot is now required to "update". So, has the "updated" yet been "installed"?

The update has been installed and the restart is required to complete the install. There is no native way of backing out of that.

If it has been installed, is there a way to prevent the "update" from happening before a reboot, so that I can "remove"/"uninstall" the pending "update"?

Pretty much the same answer as above. In fact, numerous other updates will not even occur until the restart has taken place. Windows tries to ensure later (in time) updates do not occur before earlier (in time) updates.

I do not want an update preview, but rather to simply ensure that all updates were finished before installing OEM drivers, to minimize interference.

You need to at least complete this sequence now before installing drivers. That is, do driver updates after.

If completely necessary, you can sometimes roll back an update and that may help.

If you have a working restore point, you may be able to roll back to a prior point. This is not always possible.