On Raspbian, I installed a different desktop environment and selected the wrong one in the terminal and when I rebooted, I went to the MATE desktop environment even though it's not installed.
I tried to right-click for the submenu or reach the terminal, but can't access anything. It's just the background and the movable mouse cursor.
What can I do to fix this?
No icons, text, menus or anything
sudo raspi-config
and select command line to get back to a terminal session? If not enabled - power off, pull the card add a file ssh to the /boot partition and reboot (Pi normally checks every time for this file thank goodness) Does ctl-alt-T work to give you a terminal? Try adding ` init=/bin/sh` to end of cmdline.txt (note leading space) keep on one line - do on another machine. Other machine can be the same Pi with a different SD running and original in an USB SD adapter.