Resetting edits in Lightroom

[T.Rees]

I am confused about Lightroom's latest upgrade in editing. Before I could open a photo, work on it, move on to another photo and come back to the first one, and if I wanted to I could reset it back to original. And now, if I do some work it's seems locked in. Do I need to import the original from my computer again?  

[Rob_Cullen]

Import again- NO!

Do you NOT have the menu from the three dots icon [...] ?

Where you can [Show Original], [Reset to Open], etc.