rebuiding erased fusion drive on mojave

Hello

Unfortunately I was unable to install Mojave on my newly created Fusion Drive although it appeared as if the system to split it worked.

In terminal I don't see a "fusion drive" but only the Macintosh Hard disk drive and after copying the Mojave install application to the apps in Mountain Lion attempting to install I receive an error telling me the Mojave application was corrupted

I was unable to download it directly from the App Store as Mountain Lion rejects my ID and password

I downloaded the app from a MacBookAir with Mojave installed, and it worked fine, also pretending I wanted to reinstall it it worked fine on the MacBookAir.

I now created a bootable USB pendrive brand new, which I formatted as Untitled, MacOsExtended Journaled and with a Guid partition.

WIlll this pen work on the newly created FUsion Drive on Mountain Lion?

THis is what terminal tells me about this Mountain Lion drive:

I tried to terminal the NVRAM using these commands:

1. sudo nvram -c and press Enter/return. Then the Administrator password and pressed Enter/return.
2. Then
3. Enter sudo shutdown -r now and pressed Enter/return.

However Mountain Lion didn't shut down and I am always unable to use the standard process to rest the PRAM from the keyboard sequence

ANy hints?

Thanks am lot

Using "diskutil list" we get this result

DO we need to link the first two (disk0s2) and (disk1S2) together and using the terminal comand

diskutil cs create lvgName and the long strings as 7C3457EF- etc are the same ...

DO we first need to erase the two drives again with disk utility and how to format them?

Thanks again and I really hope to find a reply

Thanks for your time however my fusion drive was never "split" (assuming that split means divided in 2 or more parts).

We (wrongly) erased the two drives, both the 120GB SSD drive, and the larger 3TB standard drive.

This mistake probably ruined the fusion-drive connection in the Imac. We erased as APFS both drive, using DIskUtility from the Command R option.

Then we installed Mojave always from the Command R on the larger 3tb drive.

Buthing the machine Mojave worked abd the problems we hac befor edidn't appear, however the smaller 120GB drive wasn't available anymore

Therefore as from several google suggestion we rebooted using Command R went to terminal and evoked:

diskutil resetFusion

but after allowing to erase pressing Y then return, terminal replied instantly as such "Operation aborted b y user".

Since we tried again various terminal commands but none worked.

As such:

diskutil cs list

which rteturned a variety of files including Dev/disk0 (120GB) and Dev/disk1 (3 TB) then various others much smaller in size

Then we attempted as follows

diskutil cs create lvgName disk0 disk1

but we got this error:

-69888

Which tell us terminal was unable to unmount the drives

At this point we dont know what else we can try although reformatting the largest drive we are able to use Mojave but the fusion-drive option was no longer available

I understand this is quite boring but I wonder if we can somehow regain the original state of the machine although we did the mistake to erase the two disks

THANKS A LOT

AND KIND REGARDS

I was finally able to merge the two disks

Still as I reinstalled the System I was forced to Mountain Lion

I hope downloading Mojave and putting it on top of ML there will be no problems.

The machine came with Sierra originally and we had plenty of problems after upgrading to Mojave

I hope this time it will work fine

I actually

Regards and thanks for your time

Thanks for your suggestion, we wrote yes and this created the original error

However doing it properly now we get this result

What can we do now?

trying

diskutil cs list

we get this error

no CoreStorager logical volume groups found

Thanks to you