C7000v2 unable to access all of the sudden

> Somehow it appears that the wifi passwords have been changed. [...]

   Many things are possible.  In some cases a power spike can corrupt
settings.

> [...] Now we are not being able to access the wifi networks from
> multiple devices. [...]

   Do you have any wired devices?

> [...] I have attempted to sign into the Genie, [...]

   You might think that "the Genie" is unambiguous, but, sadly,  Netgear
(ever helpful) uses the name "Genie" for more than one thing.  Netgear
routers have a web-browser interface called "Genie", and Netgear offers
application programs for various computers/tablets/phones, which are
also called "Genie".  I'd stick with the web-browser interface.  What,
exactly, are you using?

> [...] but I am told my password is incorrect... and I've tried all I
> can think of.

   You might be amazed at how little the non-psychics here know about
what you can think of.  If the default "admin" password ("password")
fails, and you can't guess what the router thinks it is now, then a
settings reset may be the only way forward.

> Should I do a full system reset? I am guessing this would mean I am
> starting all the way over from the beginning. Do you have other options
> to recommend?

   Unless something else works.  It would.  Not really.

   Just to be clear, visit http://netgear.com/support , put in your
model number, and look for Documentation.  Get the User Manual.  Look
for "Types of Logins".  With a wired device, the only mystery would be
the "admin" password.  With a wireless device, you need wireless-network
access before you can even get to a bad "admin" password.