How to get Linux Mint to auto start?

[Joe Lowder]

On one of my Linux Mint computers, it has auto-start
so no login is required, and it has different wallpaper
backgrounds on different virtual desktops.

But I cannot get either of those features to work on
my Linux Mint 18.3 KDE laptop. Why? And how can I
get these two important features to work?

At the following link, I have combined three screen-shots
to show the current settings in which the login theme
states: "You will be asked to authenticate ... " etc.

http://www.upquick.com/temp/settings.jpg

I am unable to find any way to disable this login so
the computer can automatically open without requiring
entering a password.

And, the only suggestion I can find online at the
link link below does not work because /usr/bin/sddm/
default-display-manager does not have
/etc/lightdm/lightdm.conf so I cannot

https://unix.stackexchange.com/questions/381785/how-do-i-enable-auto-login-in-mint-18

What do I need to do to enable an autologin so the system
does not require entering a password every time I open
the laptop?

And what do I need to do to get different wallpapers
on each different virtual desktop to work like it does
on my other Linux Mint computer?