Questions about file versioning (basic)

Running Nextcloud 23.0.8 on a hosted service

The Versions app 1.16.0 is enabled

If I create a file on a synced machine I see the file appear in Nextcloud and in the Details section under activity I see that the file has been created

I then modify and save the file a couple of times on the synced machine and I see Changed by Activity in the Details in Nextcloud, and If I click the versions tab I see the versions and can recover an old version and on the synced machine I see the recovered data.

So Versioning is working as expected.

However If I look at a file created and changed many times 4 months ago, I see No activity remarks and no versions against that file.

2 Months ago we were upgraded from Nextcloud 22 to 23.

We have 500Gb of space and about 250Gb of data being synced and less than 1% of the data changes in any month

Nextcloud sync client shows 433 Gb of 500 Gb being used

My questions are

  1. What could cause a file that was modified 4 months ago to have no Activity and no Versions showing? (Could/would the upgrade have deleted that data)?

  2. Is there any way to quantify how much data is taken up in Versions?

  3. Is there a log somewhere that shows which old flie versions have been removed by the system to save space?