How to revert to older version of Cubase?

Is any update planned for this year?
I am experiencing so many difficulties with Cubase Pro 10.5.20 that I found myself checking for prices for Ableton. I have Logic and Pro tools *and Maschine), but I am using Cubase since 1996, and believe you me, I had less issues on simple Atari ST than with this.
Plugins not loading.
64 bit plugins not working, masking issues with internal devices that work though plugins (like Elektrons Overbridge - it works in every DAW except Cubase).
Cubase crashing when idle. Or anytime, really, random.
I thought maybe it was my computer - same behaviour on both Imac and Macbook Pro.
It feels like sloppy first attempt, not like industry standard. I am seriously considering migrating all together to other DAW. My clients mostly use PT and some of them use Nuendo, middleware that I work with is more compatible with Cubase than with anything else but constant crashing is not worth it.
Steinberg, you are going to loose customers.
I would also like to know how can I revert to version 8.5. I still have it installed, but my licence has been overwritten with the 10.5. one. Can someone please instruct how can I obtain back my 8.5 licence. Thanks.

Your 10.5 license works for any lower version number.

On Windows installing 10 or 10.5 do not disable previous versions of Cubase. I can still access 9.5 or 9 should I need them for one reason or another. I am not sure that it is any different on an Apple Mac.

No it does not. Please see the screenshot.

That is not a License error, but a eLicenser application error. Something is wrong with the install.
Try downloading the newest version of eLicenser, install that and then run a maintenance.

Updated , it works ty!