factory setting

Do you have a Time Machine backup to Restore to/from?

https://support.apple.com/guide/mac-help/revert-to-a-previous-macos-version-mh15216/mac

If not you should set it up, but we'd need more info on your problem to fix it.

No matter what I do, in Recovery, I'm unable to delete three small partitions. Erase, Restore and no DELETE..,Only Apple would do something like this. Windows is so easy to delete a volume and yet here on a Mac I've spent ovet five hours trying to restore my 2019 27'' Imac to the One Terabye it came with , not these little partitions I don't even know how they appeared on my system.

But it's impossible to delete them.

In recovery nothing works...So how do I delete these poartitiions?

You cannot restore an Imac to Factory Settings......Mac has a weird Partition Table that makes it impossible to delete a Partition to factory settings. I've tried for hours to delete a three small partitions in recovery to no avail.

Hello,

https://support.apple.com/en-us/HT201065

Any luck?

Restore mini Mac to factory settings