Firebase's Cloud Firestore Free Quota Run Out Permanently Once Exceeded?

It was stated on Firebase that users can monitor their quotas using App Engine. My concern is, in order to use this, do I have to be using a paid billing account or can a free account user monitor his/her quotas if using the app engine?

I'm using the free plan, haven't set up a paid billing account, yet I can see the usage at https://console.cloud.google.com/appengine/quotadetails

A good answer is available here: Firebase storage Quota has been exceeded

Résumé: your app won't work until (1) quota are (automatically) reset, or (2) you upgrade to the paid account.

Btw, note that each document in a query counts as a read, and the quota are determined among other thanks to the number of reads. Think to cache data, using Android preferences in the app you develop, for example.

So, only based on my understanding of the quoted above answer:

Will that free quota be permanently gone (never to be accessed again) after exceeding it for the first time.

No

Will I now be automatically charged after exceeding the free quota? (even though I have never signed up for billing)

No

Since I am using the free tier quota and haven't signed up for billing, I'll just be restricted from communicating with the backend until I stop exceeding the free quota limits?

Yes

Will the free quota still reset at midnight as long as I make sure to stop exceeding the free quota limits?

Didn't really understand ; your free quota will be reset automatically at a given horodata (normally explained in the Google documentation of Firebase/Firestore).