The solution to both problems is to produce a workprint from the camera negative and edit with that. This inverts the negative image and gives you a copy that you can play with freely.
Watching someone editing on a Steenbeck [0], you will quickly see the importance of not editing the camera negative directly.
Once the edit decisions are finalized, the original camera negative is carefully cut and spliced to match the workprint, and a pristine "answer print" is struck from the edited camera negative. Traditionally, this is also where color timing is done—the printer lights can be configured to balance different shots and scenes as the answer print is being made.
The final release prints are usually third-generation copies (if you don't count the camera negative as a copy)—(1) a handful of interpositives are made from the original camera negative following the exact procedure used to make the answer print, then (2) internegatives are struck from the interpositives, and (3) a large number of release prints can be struck from the internegatives.
A notable exception to this was the release of Dunkirk (2017). The 37 IMAX screens in the world [1] that were exhibiting a 15-perf 70mm film print were actually showing a first-generation copy struck directly from the original camera negative.
(All that said, it is possible to shoot on reversal film, which is positive out of the camera, and can be edited and projected directly. Also, I've never edited a film like this myself and likely got a few things wrong—so take this with a grain of salt.)
[0] https://www.youtube.com/watch?v=dUxbfiZ_-9Y [1] https://www.gizmodo.com.au/2017/07/imax-melbourne-is-the-onl...