I don't get any security from the master password or primary password because I set it on my mozila browser but when I open mozila, the browser asks to enter the password if you cancel, also I can visit my Facebook and personal mail id. actually, I used two browsers for personal use, I prefer to use mozila only for my primary passport but now it's not worthy .
The Firefox login is a sync function that standard default Browser doesn't ask for when just using the Browser. So if you can't remember or reset your primary email login there isn't much that others users on here can do. And if you can't access the Primary email used for the login then that is a lost account since only the user themselves would know the password.
The Primary Password is only used to unlock the passwords stored in the Password Manager and is used locally (not part of Sync) and is profile specific.
Canceling the PP prompt merely disables accessing the encrypted logins, but doesn't block access to Firefox. Note that Session Restore include cookies from open tabs, so if you reopen your tabs via "Settings -> General -> Open previous windows and tabs" or via "History -> Restore Previous Session" then your are still logged in.