Update: The retired, out-of-support Internet Explorer 11 desktop application has been permanently disabled through a Microsoft Edge update on certain versions of Windows 10. Based on...
Let me see if I can help answer some of your questions:
A1: The progressive redirection of devices during that initial phase will not happen due to a Windows Update. At this time, we are not going into details on the exact mechanism other than that during this phase it will not be cause by a Windows Update meaning customers should not plan to skip Windows Updates to avoid it. Doing so presents a security risk and would be ineffective in preventing the redirection.
A2: When a device is redirected, the user will get a redirection message if they try to open IE and will instead be redirected to Microsoft Edge. When in Microsoft Edge with IE mode set up, any sites on the org's enterprise site list will open in IE mode while all sites on not the enterprise site list will use the modern engine. Organizations should prepare for this by setting up IE mode in Microsoft Edge as soon as possible if they have not done so already.
Here is the full response for that experience:
During the redirection phase, users will experience the following:
When a user tries to open IE11, they will see a message informing them that they are being redirected to Microsoft Edge. Clicking “Continue” will launch Microsoft Edge. This is an example of a message a user might see:
The IE11 icon will remain in the Start Menu, and on the taskbar and desktop (if present), but clicking on any will redirect to Microsoft Edge.
When users try to launch shortcuts or file associations that use IE11, they will be redirected to open the same file/URL in Microsoft Edge.
When users try to launch IE11 by directly invoking the iexplore.exe binary, Microsoft Edge will launch instead.