It all really boils down to how updates are applied. Some you can delete, others you should not. I’ll review the different types.
CPUs may not be getting faster as quickly as they once did, but Moore’s law isn’t really about speed; it’s about circuitry. We’re still improving in many other ways.
The bad guys can do anything they want to your computer if they can gain access.
You’re missing your boot loader. This may mean serious hardware problems… or perhaps just something forgetful on your part!
A clean install is going to get you a cleaner operating system.