quizzes: expand all 35 quizzes to 15 questions each

OPS-1 through OPS-10, OS-2, OS-3 went from 5 → 15.
OS-1, OS-4 through OS-11, SEC-1 through SEC-11, TRB-1 through TRB-4 went from 7 → 15.
Questions cover exam-weight scenarios not duplicated from original content.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

quizzes/OS-6-quiz.md

@@ -56,6 +56,62 @@ B. `chkdsk`
 C. `ms-settings:`  
 D. `whoami`  
 
+8. Which command opens the System Properties dialog (includes computer name and domain info)?
+
+A. `appwiz.cpl`  
+B. `sysdm.cpl`  
+C. `ncpa.cpl`  
+D. `firewall.cpl`  
+
+9. Which command opens Windows Firewall with Advanced Security?
+
+A. `firewall.cpl`  
+B. `wf.msc`  
+C. `ncpa.cpl`  
+D. `eventvwr.msc`  
+
+10. A technician needs to add the Telnet Client feature. Which Control Panel section is most appropriate?
+
+A. Programs and Features > Turn Windows features on or off  
+B. Device Manager  
+C. Power Options  
+D. File Explorer Options  
+
+11. Which command opens the advanced User Accounts dialog?
+
+A. `control userpasswords2`  
+B. `ncpa.cpl`  
+C. `appwiz.cpl`  
+D. `ms-settings:`  
+
+12. A user reports that file extensions are not shown in File Explorer. Which setting controls this?
+
+A. Power Options  
+B. Device Manager  
+C. File Explorer Options > View > Hide extensions  
+D. Internet Options  
+
+13. Which command opens the classic Control Panel?
+
+A. `ms-settings:`  
+B. `eventvwr.msc`  
+C. `control`  
+D. `diskmgmt.msc`  
+
+14. Which command opens Event Viewer?
+
+A. `perfmon.msc`  
+B. `services.msc`  
+C. `diskmgmt.msc`  
+D. `eventvwr.msc`  
+
+15. A technician wants to configure Windows to require a password after the screensaver activates. Where is this setting found?
+
+A. Device Manager  
+B. Personalization > Lock Screen or Screen Saver settings  
+C. Network Connections  
+D. Programs and Features  
+
 ## Answer Key For Instructor
 
 1. B
@@ -65,4 +121,12 @@ D. `whoami`
 5. B
 6. D
 7. C
+8. B
+9. B
+10. A
+11. A
+12. C
+13. C
+14. D
+15. B