Disclaimer: This discussion is only relevant for those who want to migrate their content from the Alpha (Legacy) app to the Beta app, and can otherwise be disregarded. Anyone onboarded from (May/June) onward will be using (pre)Beta from the start.
The migration will be done on your local desktop device from app to app using the data stored on your HD, and only synced to the node after this.
Export account in Legacy app → install & open Beta app → import account to Beta app
Objects that aren’t synced to your desktop device, won’t be included in your export file, and thus won’t return in the Beta version.
This is because the Beta app is entirely new software / sync architecture and the Beta backup node is starting from a blank slate. To clarify: accounts won’t be migrated on the node level (Legacy node → Beta node).
To aid the migration process, the Legacy app will receive a version update with proper account export functionality.
The Legacy node / sync mechanism will continue working, so you can always keep using it and if unsynced Objects reappear, you can do the migration later. (It is not recommended to do the import more than once though, to avoid overwriting new content.)
You could also add object content manually via copy/paste, and rebuild Sets and Relations from scratch. There’s a chance that later on (no promises), it might be possible to export individual objects in the legacy app, but for now this functionality hasn’t been developed (will notify Community in this case).

Regarding mobile sync: you’ll also need to install the beta app on your mobile devices, and as long as your Objects are synced on your desktop prior to your Legacy export/import to Beta, they will resync to your mobile Beta app.
Optimal device synchronization (and collaboration) is the primary agenda of Anysync, to prevent these kind of problems from happening in the future.
There’s been obstacles along the way, but we can’t thank you all enough for your efforts. It’s why we need our amazing Community; to put the app to the test and build the best Anytype we can! 

