Download the earlier version from the Creative Cloud app.
It's always wise to keep the previous version when updating until you get used to it (and also, maybe any plug-ins you have may not work with the new version).
To deal with your issues with the new version, which OS version do you have?
The tool box appears and disappears by pressing the tab key. Also try resetting your Workspace to see if that helps or try resetting your Photoshop preferences, which you can do under the General tab in Photoshop preferences.