Mac OS for iMac 2020

[Mahty]

I understand that the new iMac 2020 ships with Mac OS X Catalina pre-installed and, as such, no earlier version of Mac OS X can be installed on the iMac 2020.

1) Is that correct?
2) When Mac OS Big Sur is released, will all iMac 2020 machines subsequently shipped be shipped with that new OS?
3) If so, will an iMac 2020 that ships with Mac OS Big Sur pre-installed have the option of being reverted back to Mac OS Catalina?

 

[CWallace]

You should be able to install an earlier version of macOS provided you have install media for said version.

I know many are running Mohave on 2019 Macs since they need 32-bit app support and I run Yosemite on a VM on my 2017 iMac 5K.

 

[casperes1996]

I know many are running Mohave on 2019 Macs since they need 32-bit app support and I run Yosemite on a VM on my 2017 iMac 5K.

Was any Mac with a Navi GPU released during the lifetime of Mojave though? I don't think so and thus doubt it has the drivers for the GPU, so I would assume Catalina is the lowest, unless you manually take the time to make it work.
That said because of Mac Pro the drivers may be functioning in Mojave now that I think about it

 

[mj_]

1) Is that correct?'
Yes.
2) When Mac OS Big Sur is released, will all iMac 2020 machines subsequently shipped be shipped with that new OS?
Yes.
3) If so, will an iMac 2020 that ships with Mac OS Big Sur pre-installed have the option of being reverted back to Mac OS Catalina?
Yes.

 

[mj_]

I know many are running Mohave on 2019 Macs since they need 32-bit app support and I run Yosemite on a VM on my 2017 iMac 5K.

The iMac 2019 was released in March of 2019, a full six months before Catalina was released. Therefore you'll have no issues at all running Mojave on an iMac 2019.