How does Creator handle multi-user access and other tidbits

How does Creator handle multi-user access and other tidbits

Hello,
So I am relatively new to Creator 5 but not to programming itself.  But I need some clarification on a few things and couldn't find this answer anywhere in the forums. Sorry for the long post but I cannot find this info anywhere.

I am heavily modifying the Help Desk app and am scripting a ton of actions. I have several clients (not part of my company) that I want to be able to use this app for their own internal use. I understand that logged in "users" will only see the records they have created within the system. But that's about as much info as I've been able to find and in some scenarios that restriction makes no sense to me; for instance while providing multi-user access.

Any help on the following questions appreciated - 

1. What DB does Creator 5 utilize on the back-end?

2. How do I isolate my clients' record sets from other clients while allowing all users (or customers?) within that one agency to view all the associated records?

3. Considering the rule that "users" only see the records they've created, how would I expose common tables I have created that provide global variable values or other data that is not specific to a specific user? 

4. How does Creator 5 manage multi-user access? I'm assuming the DB is handling all of the heavy lifting of real-time shared data access but is there anything I need to be doing? i.e. creating a key value unique to each of my clients that isolates their data records from other client's data records?  In the original design of the Help Desk app I am modifying it uses the Firm's name as the unique identifier. But I noticed it is not part of fetch commands so not sure how it keeps records unique within each Firm.

5. I would be utilizing the higher subscription plans that allow for unlimited records but I am not clear on how the record limitations on a per-user basis is enforced. And how are "customer" log-ins managed regarding record counts? On that same note, are my clients going to have to have a paid ZOHO subscription or can I just purchase the customer login pack each month? My clients will not need access to anything else within the ZOHO ecosphere other than my application.

I've looked at the permission sets and roles but I don't see how they could help in isolating client data sets from other clients.

In a nutshell, how do I make my application available to multiple clients while only exposing that particular client's data set to all associated users (or is it customers?) that are affiliated with that client?

I hope this makes sense and I appreciate any assistance!
Doug