To add, I have created some custom fields in home page of my subdomain sites. The three custom fields I have created are
I do not see these custom fields also in General Options -> Search in custom fields (Available public custom fields types)
I am in effect not able to search multisite.
I know I tested this functionality earlier and it was working. I refreshed the installation with the latest version of wordpress, and now it is not working. Not sure, if I have missed any setting.