Ok, without internet surly the log uploader doesn’t work.
Generally for security and feature updates it is recommended to keep the device connected to internet.
To reset Kodi (which is the main part you tinker with) this would do full reset
Let’s test with Kodi default settings. Enter the following commands with an SSH connection.
systemctl stop mediacenter
mv ~/.kodi ~/kodi.bak
systemctl start mediacenter
If needed you can restore:
systemctl stop mediacenter
mv ~/.kodi ~/kodi.bk2
mv ~/kodi.bak ~/.kodi
systemctl start mediacenter
If your original setup was restored as expected and you want get rid of the unneeded clean install you can delete that with the following command.
rm -r ~/kodi.bk2
For a full reset including the OS you would need to reinstall via USB or SDCard.
There is no real list of commands to use but basically OSMC is based on Debian as OS and Kodi as the Media Center.
Here is a cheatsheet and some tutorials for how to navigate in a Linux shell: Cheatsheets and Tutorials for users new to Linux based operating systems