In a PC:
right click the file -> Properties -> Previous Versions TAB

If you moved or copied the file, it won't work

If you set the empty SKP's Model Info > Units to meters, with say 3dp and no units displayed you can input all of you dimensions as if they are centimeters [or even millimeters provided you are consistent] - thus you'll avoid the issues around the inability to make tiny facets on some meshing operations.
Once you are done... IF you must make it back into the 'real' size then draw a temporary line 1 'unit' long [actually it's 1m long, but from your viewpoint it's 1cm !]; now reset your Model Info > Units as desired; now in the Model run the Tapemeasure tool and click on the two ends of the temporary line and immediately type in 1cm, when prompted say 'Yes' to scale the entire model... everything in the SKP is now the right sizes in cm - and the now very tiny facets can exist, although their creation was not possible without the 'units/scaling' trick earlier...

PS:
You can use the Scale tool as Gaieus suggests BUT then any groups or components will be scaled BUT their original size is unchanged [unless you do further work] - unlike with the Tapemeasure re-scale trick...

View your model in a Style with a distinctly colored back-face-material - say bright-blue.
Now view your model in Monochrome mode and any reversed faces will stand out.
As has been said select them and right-click context-menu Reverse-Face to flip them.
There are also many scripts available to flip such faces from simple flippers to swapping over front/back materials as well.
If the face forms part of a 'solid' [probably required in the export you are doing] then selecting one correctly oriented face and using the context-menu Orient-Faces will flip all of the connected faces to be the same orientation - however if it's not solid you can get odd results as three faces on one edge can never be oriented consistently - one will also be 'wrong' !