SHIFT+CONTROL+Z not working and other bugs

Shift+CTRL+Z is the Redo command. You can use this only after you have already undone (CTRL+Z) an action. This is used to "undo" an undo. Check your History panel to verify there are greyed out history states below your currently selected state. Use this shortcut to navigate those steps.

If the Remove Tool stops working until you restart the application, the most likely cause is the system running out of memory for Photoshop. Closing and reopening the application clears out the temporary memory Photoshop has been holding on to, which can accumulate over time as you use memory intensive features. Check your current Performance settings in the Photoshop Preferences and make sure that you have plenty of free hard drive which is much greater than that setting (2 to 3 times is a decent rule of thumb, but more is always better). You can also check Task Manager to see what the current memory usage is.

Remove Background isn't a generative AI tool. It is just a Quick Action, which is a single button press to perform multiple steps. In this case it performs: Select > Subject, Inverse Selection, and applies a layer mask. None of this creates with AI and would thus not trigger Community Guideline messaging. Are you using some other feature instead? Like Generate Background? Would you be able to post a screen shot of what you are trying to use the generative function on so understand why it might report an issue?