How to undo "upload new version"? Is it possible

Hi Ronald, 

Welcome to Box Community and glad to help! 

You can access the file's previous version through file version history. File version history displays in the activity sidebar to the right of the file preview.

Each file version also displays with a more actions ellipsis (…). Click the ellipsis to display a menu of actions you can take. The range of actions you can take varies somewhat based on your permissions, but typically, you can:

• preview a prior version by clicking Preview.
• download a specific file version by clicking Download.
• promote an earlier version of the file to be the most current by clicking Make Current.
• delete a file version by clicking Delete.

Note

With the exception of customers of Box Governance, the number of file versions that Box saves is limited. The maximum number of prior file versions you can access corresponds to your Box account type:

• Personal Free - 1 Version
• Personal Pro - 10 Versions
• Starter - 25 Versions
• Business/Business Plus - 50 Versions
• Enterprise - 100 Versions

Customers of Box Governance have the additional option of saving an unlimited number of file versions.

In reference to this, please feel free to visit this helpful article. 

Hope it helps!