Deleted APFS volume after erasing Macintosh HD

I created a big problem doing a simple procedure.

I was erasing "Macintosh HD" on my older iMac in order to Reinstall OS, and to give that iMac to my daughter.

Used Power+Command+R > Disk Utility.

So, I erased "Macintosh HD". Then I saw some 5 GB data left, but I didn't see the sub-volume Macintosh HD Data.

But despite that, I clicked on Minus sign for the Volume in the menu bar, to delete APFS volume.

I realized I did something bad... but decided to click "First Aid" (next to Volume(+/-).

It did something and then probably asked to enter a name for a volume, so I entered "Macintosh HD".

NOW, under 'INTERNAL', "Macintosh HD" is gone.

Instead "Macintosh HD" is this: APPLE HDD HTS541010A9....(SATA Internal Physical Disk - GUID Partition Map), 1TB.

and right underneath: "CONTAINER disk3".

Clicking it shows in main window: APFS Container, and further on the right "1 TB, shared by 3 volumes"

Under "DISK IMAGES":

"macOS Base System", and underneath "Macintosh HD" (greyed out).

Clicking "macOS Base System" shows: "APFS System Volume-APFS.......1.16 GB, shared by 3 volumes0"

Clicking the greyed out "Macintosh HD" shows in the main window: an ORANGE icon of "Macintosh HD" , and underneath says: "APFS Volume - APFS..........1.16 GB, shared by 3 volumes".

Then further down(in the main window):........says: NOT MOUNTED (greyed out), and some more details:

Capacity...... 1.16 GB

Available:......zero kb

Used............. --

Type..........APFS Volume

Owners.....disabled

Connection....disk image

Device...........disk2s3

I realize it's a mess, can it be fixed ? What should I do please ?

THANKS!