Where is the session data stored?

2.  Where is the session data stored ? and how secure is the data and is will it be accessible by others. 

Session data is stored to our servers and retrievable through the session URL only. The data is secured, but then again, someone who knows the session URL will be able to view the data.

The session URL is hard to guess so I think that's not a problem at all. But not unless your user filled the form using a shared PC. If that is the case, you should advise them to clear the browsing history before leaving the computer to others.

Thanks