Android Questions

Couple of questions about the Android distro.

  1. Its under version 7 with security patches being from 2015 (I know there is a note to say they are working on a version 9 edition) but how at risk is it to run it on the internet ? I know Android in based on Linux so it has a decent start but surely if it is that out of date its open to exploit ??

  2. How can i completely remove the pre-installed apps ?

  3. How do you power down the system when using a keyboard and mouse ?