TurboCAD

TurboCad is not compatible with Big Sur. It only works with Catalina (10.15) and earlier:

TurboCAD Mac System Requirements:

Macintosh® OS 10.11 through 10.15 or higher

(From the TurboCad website)

Depending on what system came with your Mac originally, you'll have to downgrade the system to Catalina or earlier in order to run TurboCad.

Old Toad wrote:

TurboCad is not compatible with Big Sur. It only works with Catalina (10.15) and earlier:

I guess you missed my post.

Big Sur Compatibility – TurboCAD v12 Mac has now been updated to be fully Big Sur Compatible.  If you are a current Version 12 owner, please contact IMSI Design at support@imsidesgin.com to receive a download link to install the Big Sur-compatible version. 

According to the website TurboCAD v12 is compatible with Big Sur.

https://www.turbocad.com/content/turbocad-mac

Whether it will run on an M1 Mac you will have to ask.

What do you mean by "ISO"? Are you the victim of a wayward spell correct?

That's the problem with tunnel vision you miss so much. I zeroed in on the OP's post and didn't even scroll down to see any others. 🤭