Best to post in the Student Edition section of the forum, as @MF states, commercial versions cannot open these files. [by design] Some of us commercial version users have [although limited] access to Student Edition.
To your question though, this is a limitation of the synchronous work flow, or rather a mind set training procedure, for when primary faces can get consumed, beyond the reach of "undo". Many Synch users are placing their rounds, especially for cases like this, in Ordered mode, to retain the original state face set, if these are still in design flux. [see attached]
....but it is still very easy to restore. Select and delete the lower fillet, then sketch new semicircles to make a protrusion.....then once made, select the resulting face and it will be editable to the size it should be.
Design Manager Streetscape Limited
Solid Edge ST9 [MP8] Classic [x2 seats]
the other tip/trick here is replace face.
So some times createing a tangent plane and replace to the plane or in this case extrude a cylindrical surface and replace to the surface.
BUt as mentioned the most prefered method is to put all treatment features in ordered.
Thank you for the solution. I will post questions to the SE section later.
Adding material through the exisiting part caused some glitch, but I could completely remove the material and resize the inner dimension to get it restored.