Eric F.9 Dropboxer

You should be able to develop this functionality through our Core API, using the /files and /files_put options. Alternatively there are many apps that have similar functionality. https://www.dropbox.com/developers/core

Are you asking for a way to allow teachers to create folders that students can upload and download files from, but cannot modify files within?

The revision numbers do not change, even as old revision are dropped after 30 days. Additionally, you should be using "rev" instead of "revision", as revision has been deprecated. https://www.dropbox.com/developers/core/docs#metadata-details

It sounds like it may be a networking error — have you been able to duplicate the issue?

Are you using our Core SDK or are you using iOS's built in document picker?

I believe you're asking how to allow users to authenticate to your Dropbox app. We use the OAuth2 flow for this (https://www.dropbox.com/developers/core/docs), which will return an access token allowing you to make calls on the user's behalf from your application.