Cookies can only be valid for one domain. By default, it's the host of the current location excluding subdomains.

If a cookie is from getmimo.com, for which of these options would the cookie be valid?

getmimo.comapp.getmimo.comgoogle.com

Exactly, by default, the cookie is only valid for the host of the current location and not valid for any other domains.

As app.getmimo.com has a different subdomain and google.com is a different domain. That means none of those are valid.