I'm Trying To Make A Quiz App Using Firebase As My Backend And Modular JavaScript As Client Side Script And I Came Across A Problem Recently.
So I Wanted To Make A Timer which shows the user how much time is left before the test ends and gets auto-submitted. But how do I implement it in such a way that the end user doesn't use the Debugger or Other Tools to manipulate this timer. Also In Firebase Rules i have ensured Write Access is disabled after the "time slot" for attempting is over.

For Example: Lets Say Test 1 is Active from 1:00pm - 12:00pm(Timeslot) and you can attempt it for 60mins for any time in this time slot. How Can I Make Sure That The Client Attempts Test For Only 60 mins and not like if he starts from 1:00 and he manipulates the time to write till 12:00pm.

How Can I Implement This? Do I Need Server Side Support Like Cloud Functions? I Didn't Want To Use Them Till Now As Sending A Request Every 1 second or 5 seconds Uses Up A Lot Of The Data Resources When This App Scales to More People. (Also That I'm Building It On Spark Plan)