If you don’t want to save changes you made to your spreadsheet since opening it or
last saving it, you can undo them.
Here are ways to undo changes:
To undo your most recent change, choose Edit > Undo.
To undo multiple changes, choose Edit > Undo multiple times. You can undo any
changes you made since opening the spreadsheet or reverting to the last saved version.
To restore changes you’ve undone using Edit > Undo, choose Edit > Redo one or
To undo all changes you made since the last time you saved your spreadsheet, choose
File > “Revert to Saved” and then click Revert.