Hi, after testing with Google assistant, decided to create a new project, so deleted the old one on the console Google site…
But in Google home control app, I still see the old test app ,it’s unlinked , but how to remove it from that list??
Just wait. It will be removed in some weeks automatically by Google.
but i deleted the old project already a month ago 
I’ve forgot the timespan Google keeps deleted projects to enable recovery. It may be 90 days, but I don’t remember exactly. If you really want to know it it’s documented somewhere by Google.
ok, 90 days is indeed not past , we will wait 
I’ve just googled it and there it says projects will be deleted after around 30 days but deletion depends on some other factors. So you can’t rely just on the count of days
interested in that “other factors”