Is it possible to download Windows 7 or 10 on iMac?

On Intel Based iMacs you have 2 options:

• Use Bootcamp to install Windows or
• Use Parallels to install Windows.

On M1 based iMacs you only have 1 option:

• Use Parallels to install Windows.

Sorry tbirdvet, your information is out of date. Parallels.com says:

Run Windows on Mac

NEW!

Parallels Desktop 16 for Mac

The fastest, easiest and most powerful application for running Windows on Mac (including the new Apple M1 chip) — without rebooting. Includes 30+ utilities to simplify everyday tasks on Mac and Windows. 

My info is not out of date. The version of Windows 10 for M1 with Parallels is the Windows ARM insider version (beta) that can be installed but not all apps work at this time. It is worth a try but until it is officially released you take a chance on 100% functionality. I have tried this on my M1 but has some bugs.

On an intel Mac, yes. On the new M1 versions, no.