Mac mini 2012 cant upgrade at all

Hi

I am running a mac mini 2012 with i5 and 16gb RAM and 500gb HDD. The only change i made to the mac is add RAM. I have used it for a long time, and now i cant install anything other than Mavericks on it.

Problem:

I used internet recovery to load Mavericks, then when i try to install El Capitan or Yosemite from app store, i get this(see attached pictures) warning. The plan is to install Catalina, but I am not jumping straight because I read somewhere that I have to be on High Sierra in order to upgrade to anything above. And from past experience with my mac, it refused to install high sierra.

History:

I have used it while it was on mavericks and kept updating it as they are released, until i reached High Sierra, after which i decided to not install Mohave, thinking it will slow it down even more.

Then there was a long while when i didn't use it regularly.

Until last year when i decided to DOWNGRADE to sierra to return back to how it used to perform.

I used a usb installer following commandline instructions to create the usb.

A possible mistake i did here is that i made the usb installer from a macbook pro running Monterey.

But it worked and I got Sierra working but then i noticed the browsers are out of date.

So I try to install High Sierra from app store but it fails in the later stages of the installation with 'couldn't be installed'.

But now something happened in the recovery that makes the mac load to the installer everytime, instead of the previous working OS.

So I try to install High Sierra using usb method several times with same results 'couldn't be installed'.

This warning comes towards the later stages, after the restart that happens mid installation.

I tried reading the logs and couldn't figure out the problem. It seemed like it couldn't find some files which led to the failure, but i am not sure if that caused the failure or something else. Disk utility doesn't find any errors in the HDD.

After this, it wouldn't install ANY mac os with the same problem as above.

I spoke to Apple support and then used the network boot to install mavericks successfully.

I would have settled for Mavericks but the browsers are out of date.

But i was unable to install any other Mac OS, even when i download from app store.

Then i installed ubuntu on it for sometime but have bluetooth problem with apple magic keyboard and touchpad, so decided to install Mac Os again.

So I used internet recovery to load Mavericks again, which leads to now.

More information:

There are two kinds of failures i experienced.

1) failure to install when the installer is running in recovery (later stage).

2) failure to install when the installer just started running in Mac Os (early stage).

This question is mainly about the 2nd kind.

in order to mitigate both failures, i have tried several things, like changing the date, keeping the device offline, changing the date to specific dates, installing using usb, formatting HDD, installing using app store... but it always fails for different reasons.

I have also noticed although i have access to the 'internet recovery', some of the components of recovery is missing from my device now. There is a Apple Diagnoostic Utility supposedly built into recovery that is missing from my mac. when i try to open it by pressing D or Option-D, nothing happens. My several attempts to install Mac Os has somehow deleted it from my system.