Downgrade Big Sur from 11.1b1 to 11.01 on another disk or volume

[haralds]

I need to do some comparison testing of an app on 11.1b1 (installed on my MacBook Pro M1) vs 11.0.1 release. Alas I upgraded before installing another partition or disk with the release version.
As usual for macOS, you cannot install an older version from the newer running version. But you used to be able to install an older version supporting the hardware from USB. This did not work.
I installed 11.01 on an external disk on another MacBook but it also refused to boot.

Does anybody have any pointer on what to try next?

 

[Gnattu]

Per Apple Support Page, you have to set Security Policy to "reduced security" to boot any version of macOS

 

[haralds]

Yup, did that to install Rogue Amoeba, too. It will not let me install an older versions - period.

 

[haralds]

Could not downgrade. But ended up "side grading" on another volume for future work. A second Big Sur volume will become the designated Beta once 11.1 goes final on the main volume.

 

[MikhailT]

IIRC, the initial releases of Big Sur doesn't support M1 that well in terms of reinstalling or downgrading on other partitions. macOS 11.1 is supposed to be the first one that does; that's why if you read the release notes for the last beta, it mentions that part.

For now, your best option is to wait it out as you said.

 

[tdar]

See the release notes for beta 2 released yesterday.

 

[haralds]

See the release notes for beta 2 released yesterday.

That was concerning booting back. This failed on trying to install. Setting up a 2nd 11.1b2 volume worked like a charm.
Going forward that will be my beta volume after 11.2 releases.