Issues with Zoho Docs

Hi,
I have availed a Free Zoho account for mails which come with Zoho docs 5Gb /user storage. The users that I have created have a few concerns with sharing docs and working on them.
1) Firstly unable to share files to external email accounts(i.e outside Zoho domain)
2) When I try the share feature multiple times some of the id's zoho docs accepts and shows that the user has read write access however there is no notification that goes to the external user of the shared file.
3) One of the users in the domain had uploaded a document which he could download once and then the document was missing from his docs.
4) When the file is shared externally the external user has to signup for a 14 days trial is a way to share the document with the external user so that the user can access the file without the signup.

Could you let me know if there are tweaks that I would have to do from the admin side or are there any limitations with the free account.

-Sharieff