You can either do backup or a snapshot in the timeshift to recover previous instances of the system. Before anything else, learn these simple procedures.

https://linuxvox.com/blog/linux-mint-system-snapshots/

https://www.fosslinux.com/102696/how-to-back-up-and-restore-your-linux-mint-system.htm

Also save this link to the Linux Mint User Guide: https://linuxmint-user-guide.readthedocs.io/en/latest/

After that, Go wild. You can also have fun trying different linux distro without installing them. All you have to do is the same usb bootloader with rufus (or etcher from linux) and just try them from the pen without install anything.

Linux mint is a baby of Ubuntu (and grandchildren of Debian), so pretty much any command or app who works there, works on mint too. The teminal have also a sort of manual preinstalled. If you type "man" plus the comand you want to check.

https://commandmasters.com/commands/man-linux/

Last tip. If you want to add more cool icons you can simply unzip/extract the icon-set folder and past them in /usr/share/icons then open the theme app and they should be there with the other