Migrating from Norton Internet Security to Norton 360

Hello All,

I'm getting a prompt sliding up from the system tray with the following alert:
"You have not completed your Norton product registration."

After some due diligence, I determined that I'm using Norton Internet Security, instead of Norton 360, so I'm running an outdated version. However, I have an active subscription for Norton 360 Deluxe Plus, therefore I'm not sure how this got overlooked, given it's running on 3 other home computers.

The following articles seem to provide the correct solution:

1. Uninstall your Norton device security product on Mac
2. Download and install your Norton device security product on Mac

However, I have the following questions:

1. Can I install Norton 360 first, and then uninstall Norton Internet Security to help reduce any potential vulnerabilities?
2. How vulnerable will my computer be to attacks during this process?
3. Since Norton Internet Security has been replaced by Norton 360, how does it still work on my computer?
4. Why would the software show having been updated in my "Applications" directory back in December if it had been discontinued?

This issue is outside my area of expertise, therefore I want to proceed with caution. Any advice or direction would be greatly appreciated.

Thanks,
Mario