Windows 2012 RDS Collection published app configuration

We have a Windows 2012 RDS collection - 1 connection broker, 2 session hosts.

I have published an application and able to access it from RD WEB without a problem. 

There are two issues:

1. When I click on the app from the RE WEB page, I see a RDP file being downloaded and I need to open it to access the app.  How do I make it so that user can just click on the app and open?

2. After the app is opened, I check the drives that the app can access by clicking FILE>OPEN.  I see the C drive of the web server is available to the users.  How do I hide it?

Thanks,