Can multiple users access the same data and applications simultaneously?

Yes, hosted applications are designed to be used by multiple users simultaneously, although certain types of data access may be restricted after the first user.  Quickbooks Pro for example, allows five simultaneous, fully functional connections to the application in multi-user mode.  A Microsoft Word document, on the other hand, can only be edited by a single user at a time.  All subsequent users open the file in read-only mode.
Of course, all application access is subject to licensing restrictions and adequate user accounts.  If you wish to give multiple users simultaneous access to your Microsoft Office files for example, each user must possess an office license, as well as their own Red Hen Remote user account.