It is possible but not recommended. MS does not support the use of multiple versions of Office on versions of Windows that have Terminal Services enabled. (Terminal Services has been renamed Remote Desktop Service in 10 and 11.)If you want to run multiple versions of Office on Windows, you should disable Remote Desktop) Personally I would suggest if you have a need for an older version, to avoid any conflicts I would run it in a VM instead of alongside the new version.
Over the years I have run into this scenario regarding 2 versions of Office. Since some dlls are common to more than one version of office, when you remove one version dlls that affect both versions are removed. It can end up in a mess. You are much better off using one version. Just my opinion as I believe it's better to be safe than sorry.
I know where you are coming from with Ofc2021. After many years of using Ofc 2007, 2021 is a culture shock and difficult to use. Luckily I have Windows 10 and 11 machines. What I did to relieve some of the pain even though I also bought 2021 for 10, was to keep 2007 in Windows 10 and then Remote Desktop from 11 into 10 if I need to use Ofc 2007. If you have only one machine then a VM would be the way to go.
