How to show original photo in Photoshop?

Hello, are you used to Lightroom?

If you did all your work without layers, and did not save the image yet, save it under another name, then open the original one again in another window, to compare as you work.

You could also use the revert function in the file menu to restore the image to its original state, and you can undo that. F12 does the same.

Here's what I like to do:

Image > Duplicate   Make a copy and work on that copy. Save that copy as you go along. That way you preserve the original or archive file.

Window > Arrange > 2-up vertical  to compare both while making adjustments to the copy.

If you have the screen space, you can make duplicates and experiment on them in multiple windows, keeping the original as the reference.

Could you please post a screenshot with the pertinent Panels (Toolbox, Layers, Channels, Options Bar, …) visible? 

If you employed a prudent workflow and

• maintained an unchanged copy in the background you can hide the other Layers by alt-clicking that Layer’s visibility icon in the Layers Panel, 

• otherwise you might be able to view the image as it was opened by clicking the snapshot in the History Panel – but be careful, one mis-click might make you lose your editing if you didn’t save properly.