The title bar of the cmd says "Administrator:Command Prompt". So, I am hoping that I am following your instructions correctly and running everything as administrator
Bravo -- correct user-id & login
Before changing the R/O:
C:\Windows\System32\drivers\etc>attrib hosts*
A R C:\Windows\System32\drivers\etc\hosts
A R C:\Windows\System32\drivers\etc\hosts-0
A R C:\Windows\System32\drivers\etc\hosts.00
A R C:\Windows\System32\drivers\etc\hosts.20200116-120718.backup
A R C:\Windows\System32\drivers\etc\hosts.20200116-121548.backup
A R C:\Windows\System32\drivers\etc\hosts.jeffs
C:\Windows\System32\drivers\etc>
change and redisplay
C:\Windows\System32\drivers\etc>attrib -r hosts
C:\Windows\System32\drivers\etc>attrib hosts*
A C:\Windows\System32\drivers\etc\hosts
A R C:\Windows\System32\drivers\etc\hosts-0
A R C:\Windows\System32\drivers\etc\hosts.00
A R C:\Windows\System32\drivers\etc\hosts.20200116-120718.backup
A R C:\Windows\System32\drivers\etc\hosts.20200116-121548.backup
A R C:\Windows\System32\drivers\etc\hosts.jeffs
In Addition, notice the SaveAs dialogue for All Files
Now add +r to protect the file
C:\Windows\System32\drivers\etc>attrib +r hosts
C:\Windows\System32\drivers\etc>attrib hosts*
A R C:\Windows\System32\drivers\etc\hosts
A R C:\Windows\System32\drivers\etc\hosts-0
A R C:\Windows\System32\drivers\etc\hosts.00
A R C:\Windows\System32\drivers\etc\hosts.20200116-120718.backup
A R C:\Windows\System32\drivers\etc\hosts.20200116-121548.backup
A R C:\Windows\System32\drivers\etc\hosts.jeffs