Why don’t you create a subfolder for Scrivener projects and point iOS Scrivener’s link there?
The Dropbox rewind function is a feature of Dropbox, not Scrivener. In theory, it should work fine. However, the internal structure of a Scrivener project is fairly complex, with subfolders and potentially hundreds of component files. We recommend using a backup protocol that allows you to revert the project as a unit, rather than counting on your ability to locate individual component files. A guide to backups for iOS Scrivener can be found here:
https://scrivener.tenderapp.com/help/kb/ios/guide-to-keeping-ios-projects-backed-up
(The Files app, discussed at the link, would also be the recommended tool for sharing iOS Scrivener projects outside of Dropbox.)
There’s also a good thread on syncing without Dropbox here: Alternatives to Dropbox (sync) - #4 by perry