1. Can administrators manage forms and answers?

I'd say yes but it's up to you.

2. I understand that staff can manage forms mean create, edit, delete form also, assign form to users, but what is manage clients’ answers?

Staff can of course view clients' answers. It's less certain whether staff should be able to change clients' answers - allowing staff to change clients' answers may cause legal problems, but on the other hand sometimes it's just much more efficient to let staff fix some typo instead of informing the client and waiting for the client to fix it. Again I'll leave this decision to you. These types of design decisions are fairly common, and which way to go depends on how you envision the application will be used.

3. In hw6.txt do we need to include testing procedure in it? Something like ‘go to this page and click this button’ or just something technical like ‘ we add @Preauthorize to saveUser method’.

Obviously you should test it, but you don't need to describe the testing procedure in hw6.txt. Something like "we add @Preauthorize to saveUser method" is enough.