Support for multiple customers

Support for multiple customers

I have a computer training company... 

When we teach individuals, we want the person to login, post questions, get answers and only see their entries.

When we teach a group at company A, we want everyone who attended class from that company to see each other's entries.  Otherwise, we'll be answering the same question 10 times for 10 people whose offices are right next to each other.

When we teach a class to company B, we want them to login without seeing the individuals or anything related to company A.

Does the Support app support this setup?

And how many customers can login if we get the Professional edition?  Are there any samples sites out there?  I'd like to try before I buy.  Too bad there's no trial.  And there any videos or screenshots on this application?

--DJ