I have a C7 and a Fibar FGD-212 dimmer which is set S0 security.
I excluded it, reset to factory, and included it again wanting to set it with no security.
Problem is I never got a menu during inclusion to set the security. I just re enrolled as a S0 security again.
As @aaiyar alluded to, you can't do it with just the C7 alone (you can thank SiLabs and their certification process for that). To expound, see here for a bit more info:
Yes
There's a link in this post that has a guide. There's a step in the guide on how to include without security. Make sure you uncheck security when pairing your z stick.