If you updated to a new WordPress version and were welcomed with error messages, unaccessible admin interface and isn't worth my time debugging this feelings, these quick steps are for you.
Returning WordPress to a previous version is safe (from a functional perspective) most of the time. You should try to update again once non-compatible plugins get fixed.
Database changes between minor WordPress versions are few, but if you don’t have any kind of disaster recovery plan in place, you’ll be in a safer position if you backup it before restoring WordPress.