Sure, if you have multiple devices with the same Apple Id, then, you can synchronize the In App Purchase.
Go to the 'Admin' tab, tap on 'Full version' buton, select you In App Purchase, and tap the 'Restore' button
Sure, you can synchronize your database with a Dropbox account
Go to the 'IO' tab, and then tap on Sync row
Sure, you can synchronize your database with a Dropbox account and share your Dropbox account with other users
Go to the 'IO' tab, and then tap on Sync row.
You can create a new Dropbox account if you don't want to use your personnal Dropbox account.
If you already have an inventory, you can import it with the 'Import' feature.
Go to the 'IO' tab, and then tap on Import button. Then follow the guidelines.
You can have several inventories in your database.
Go to the 'Admin' tab, and tap on the 'Inventories' button.
Go to the 'Admin' tab, and tap on the 'Inventories' button. Then select the inventory you want to clone.