How do I recover lost Calendar app events from iCloud?

At the beginning of the month all my information was still in my calendar. Around the 16th March I went onto my calendar to find it only the national holidays were on the calendar.

i only use the iCloud to store my calendar information so I tried going on settings into my iCloud section and I tired if off and back on again and then restarted my phone. This brought back only the reoccurring events but none of the one off events.

I have sat through over 3 hours on the phone with Apple support. They tried the same thing, they tried going on my iCloud account to restore an old version but apparently the only version that was backed up was from the 16th March so it didn’t bring back anything. They looked in my settings under the calendar app to check it was saving the information in my iCloud not a secondary account which it was. They also checked it was syncing all events and that the default calendar was iCloud. They looked in the calendar app to see the settings here. We then restarted my phone. When none of this worked they contacted their engineers to see if they could recall an old version of my calendar for me. They were also unsuccessful with this.

I have used my iCloud calendar for maybe the last 6 years of my life, it has all my personal and a lot of my professional appointments as well as medical once. They were able to recall none of this. If anyone is able to help me at all it would be really appreciated, thank you.

[Re-Titled by Moderator]